Macbeth should be protecting Duncan, not trying to kill him.  Finally, as far as Duncan is specifically concerened, he has been a good king.  He has not abused his powers and has been generous.  Macbeth recognizes that the only reason he wants to kill Duncan is his own ambition to be king - Duncan does not deserve to die.

Macbeth still has cold feet about killing Duncan. He's had the dragon seed of ambition planted in his mind by the three witches and Lady Macbeth, but he's still worried about the potential consequences of carrying out such a murderous act of treachery. It is this nagging worry that forms the basis of his soliloquy in act 1, scene 7, for which I provide a rough translation below:

If I'm going to kill Duncan, it's best to get it over with as soon as possible. If there would be no consequences to the murder, then that would be great; I'd gladly do it, even if it meant putting my soul in danger. However, in this world, it's different: actions have consequences, and bloody actions have bloody consequences which can come back to haunt us. What goes around comes around.

I'm a member of Duncan's extended family as well as a servant, so I should be protecting him. As his host I should be closing the door in his murderer's face, not murdering him myself. What's more, if I kill Duncan, his virtuous legacy will live on, acting as a constant reminder of my murderous deed, as will the tears of the people, who will weep in pity for their fallen king.

I can't spur myself to action. The only thing that motivates me is an intense desire for power, but that tends to bring people down, causing disaster.

In this soliloquy, Macbeth reviews the many reasons he has not to move forward with the plan to kill Duncan as well as the one reason that he has to actually go through with the murder.

First, he considers that simply committing the murder will not be enough to make him the king: in other words, it will not be "done quickly."  He considers the fact that if he could simply commit this one "blow" and achieve his destiny without consequence, it would be a lot easier to go on and risk his eternal soul.

Next, Macbeth considers the fact that, here on earth, there are punishments, consequences for the type of behavior he's considering.  For one, when a person commits a violent act, he inadvertently teaches others how to commit violence, and this can come back to harm the initial perpetrator (i.e. him).  Though this would be justice, it could spell death for him.

He considers the fact that Duncan is both his relative and his king as well as his guest, and all these relationships should mean that Macbeth actually protects Duncan from violence, not commits the violence himself.  Further, Duncan is such a humble, virtuous leader that his legacy would live on and on, and his death will be such a great sorrow to everyone in the kingdom. 

Finally, Macbeth claims that he can think of no reason or motivation to kill Duncan aside from his own "Vaulting ambition" which seems to compel him to rush ahead and, perhaps, rush right into danger. 

Macbeth's soliloquy at the end of act 2, scene 1 is the famous "dagger" speech. Fueled by his ambition, Macbeth plans to kill the king in his sleep in order to become the king himself, but in this speech he expresses hesitancy and guilt at the thought of carrying through with his plans.

This guilt manifests in a hallucination of a dagger. Macbeth narrates his actions as he imagines that he sees the fatal instrument in the air in front of him ("Is this a dagger which I see before me?"), yet when he tries to grab the handle he discovers he cannot ("I have thee not, and yet I see thee still"). In response to this vision he draws his own dagger from his belt as a point of comparison. This will be the weapon that he uses to kill King Duncan. In the lines,

Thou marshall'st me the way that I was going;

And such an instrument I was to use.

it becomes clear that Macbeth believes the hallucination to be a portent, guiding him towards the murder he is about to commit. It points his way forward.

As he continues to hallucinate, the "dagger of the mind" begins to drip with blood, a symbol of his guilt. The tone of the monologue is fearful, with Macbeth repeatedly trying to snap out of it, so to speak, and convince himself that he's just seeing things:

There's no such thing:

It is the bloody business which informs

Thus to mine eyes.

Though here Macbeth seems to argue that the hallucination is caused by his impending crime, he then goes on to talk about witches and witchcraft. The fearful tone combined with the violent imagery makes it unclear whether this hallucination is supernatural in origin or indeed just a manifestation of Macbeth's guilty conscience. Both are possible within the world of the play.

Macbeth's musings on the vision and the deed he is about to commit are interrupted by the sound of a bell, a signal from his wife that the king's guards are drugged to sleep and the time for action is now. If the hallucinated dagger was a portent meant to warn Macbeth not to murder the king, he ultimately ignores it, proceeding with his original plan despite any guilt or hesitation he may feel.

I go, and it is done; the bell invites me.
Hear it not, Duncan; for it is a knell
That summons thee to heaven or to hell.

In this soliloquy, Macbeth is headed toward King Duncan's chamber to commit regicide when a vision of a bloody dagger suddenly appears before him. A bit confused, Macbeth reaches for the floating dagger, but his hand only passes through empty air. The dagger points him toward Duncan's chamber, seeming to bid him to take action while the king and the rest of the world are sleeping. Macbeth decides that the dagger is a hallucination brought about by his knowledge of the wicked deed he is about to commit. He hears a bell tolling, a signal that it is time for him to proceed, and heads to Duncan's chamber.

At the end of this soliloquy, we are reminded that Macbeth has fears of his own. The longer he contemplates aloud the significance of this ghostly and bloody dagger, the more he hesitates and risks losing his conviction ("Words to the heat of deeds too cold breath gives"). It's not apparent that he is necessarily a wholly evil man—as demonstrated by the mental torment and fear he expresses in the moments preceding the king's murder. Rather, Macbeth seems inclined to follow the prompting of others, from his wife to this ghostly dagger that urges him forward. This hesitation will vanish after the murder of the king, which marks a distinct turning point in Macbeth's character development. Soon afterward, Macbeth devolves into a bloodthirsty tyrant who is willing to kill—seemingly without conscience—to keep the throne.

This soliloquy offers the audience a glimpse of Macbeth's bloody act, yet like much of the violence of the play, the actual murder takes place off stage and out of the audience's view. Earlier in the play, Macbeth rhetorically asks his eyes to blind themselves to the bloody acts his hands want to commit ("The eye wink at the hand; yet let that be, / Which the eye fears, when it is done, to see"). Duncan's offstage death seems to echo this sentiment, shielding the audience to the brutal reality of Macbeth's actions. This perhaps allows the audience sympathize with Macbeth for a bit longer, yet it also leaves room for them to imagine the worst, which highlights the ambiguity and tension in how Macbeth is presented to the audience. There is the hesitant, contemplative Macbeth, who acts only at the urging of others, like the witches and his wife. Then there is the ambitious and wicked Macbeth, whose inherent corruption leads him to form a murderous plot from the instant he hears the witches' prophecy. It's left up to the audience to decide which side of Macbeth is the real one.

In Shakespeare's Macbeth, Act Three, scene one, Macbeth delivers a soliloquy with regard to being King and the dangers that threaten his position, namely his close friend Banquo.

Macbeth states that to be King is nothing if he cannot safely be so. His biggest worry at this point is Banquo, who was present when the witches made their predictions. This incident would naturally raise questions in Banquo's mind about what Macbeth did to make the predictions come true. Macbeth fears Banquo's "royal nature," in essence, his integrity. Banquo has the courage to take a stand and is smart enough to do so in safety. Banquo, Macbeth admits, is the only person he fears, and Macbeth's actions would be "despised" in Banquo's sight—the same way Caesar felt about Mark Antony (or so they say).

To be thus is nothing,

But to be safely thus. Our fears in Banquo

Stick deep, and in his royalty of nature

Reigns that which would be fear'd. ’Tis much he dares, (55)

And, to that dauntless temper of his mind,

He hath a wisdom that doth guide his valor

To act in safety. There is none but he

Whose being I do fear; and under him

My genius is rebuked, as it is said (60)

Mark Antony's was by Caesar.

Macbeth recalls that Banquo scolded the three witches ("sisters") when the first "predicted" that Macbeth would be king, that they should speak to him also. Like prophets, the witches declared that while Banquo would not be king, he would father a line of kings. Macbeth understands now that he will never have children to pass his crown to ("fruitless crown") and his power will be taken from him ("barren scepter"), never to be given to his son: he has no children.

He chid the sisters,

When first they put the name of King upon me,

And bade them speak to him; then prophet-like

They hail'd him father to a line of kings:

Upon my head they placed a fruitless crown(65)

And put a barren sceptre in my gripe,

Thence to be wrench'd with an unlineal hand,

No son of mine succeeding.

If this is the case, Macbeth reasons, he has sold his soul to the powers of darkness—in killing Duncan, a king—so he could be King, but more so, that Banquo's descendants will come to the throne. Seemingly for nothing, Macbeth has lost his peace of mind, has lost his soul ("his eternal jewel") to "man's common enemy" (the Devil), just to make Banquo's "issue" (descendants) kings. Rather than see this happen, Macbeth is prepared to fight Fate to the death if necessary, to keep the witches' prediction for Banquo from coming true.

If't be so,

For Banquo's issue have I filed my mind,

For them the gracious Duncan have I murdered, (70)

Put rancors in the vessel of my peace

Only for them, and mine eternal jewel

Given to the common enemy of man,

To make them kings, the seed of Banquo kings!

Rather than so, come, Fate, into the list, (75)

And champion me to the utterance!

I assume that you are referring to the speech Macbeth makes at the end of Act Four, scene one, in Shakespeare's play, Macbeth, when Macbeth decides how he will proceed with the new information he has received, specifically from Lennox regarding Macduff's flight to England.

By going to England, Macduff, a good and decent man who loves his country, is branded a traitor—Macbeth knows that Malcolm is in England enjoying the hospitality and protection of Edward the Confessor.

Macbeth's speech is delivered as an "aside," so that no one else on stage can hear him, but the audience knows what he is thinking. Macbeth first comments (as he personifies time, as "anticipating") that "Time" knows Macbeth's plans already. He admits that putting off one's actions never brings about the results someone wants. He promises that from this time on, if he conceives a plan, he will act on it—carry it out—instantly.

[Aside.] Time, thou anticipatest my dread exploits.

The flighty purpose never is o'ertook

Unless the deed go with it. From this moment

The very firstlings of my heart shall be

The firstlings of my hand. And even now,

To crown my thoughts with acts, be it thought and done…  (IV.i.61-65)

Macbeth intends to start joining his thought and actions right now. Macbeth plans to surprise and seize Macduff's castle and its occupants, and then kill anyone in there at that time: Macduff's wife, his children and his servants—anyone that can be connected to Macduff in any way. We see in this that Macbeth has truly gone mad —killing not Macduff, but his family—just to punish Macduff's rejection of Macbeth as his King, as well as the true King of Scotland.

The castle of Macduff I will surprise,

Seize upon Fife; give to the edge o’ the sword

His wife, his babes, and all unfortunate souls

That trace him in his line. (168-170)

Macbeth promises that he will not "boast" foolishly about what he intends to do, but will carry out this deadly deed before he has a chance to think about it or before his temper cools down. He wants no more visions, now; he just wants to strike quickly.

No boasting like a fool;

This deed I'll do before this purpose cool.

But no more sights!–Where are these gentlemen?

Come, bring me where they are. (170-173)

The witches' second set of predictions have given Macbeth a sense of invincibility—but it is a "false sense of security," as Hecate had hoped. Macbeth is just as committed to his purpose as ever before. He believes no one can touch him.

[eNotes editors are only permitted to answer one question per posting. Additional questions should be posted separately.]

In Shakespeare's Macbeth, Macbeth's soliloquy found in Act Two, scene one, is often referred to as the "dagger" scene. Macbeth imagines a dagger hovering before him. This element of the supernatural is the first, seen before Duncan is murdered, because Macbeth has upset the balance of the universe by killing the God-chosen King.

First Macbeth wonders if he can believe his eyes. He also wonders if the dagger is an image or if it has substance—until he tries to grab it and is unsuccessful. Macbeth then wonders if the dagger is not the result of his "fevered brain" that is overwrought.

Is this a dagger which I see before me,

The handle toward my hand? Come, let me clutch thee.

I have thee not, and yet I see thee still.

Art thou not, fatal vision, sensible

To feeling as to sight? Or art thou but (45)

A dagger of the mind, a false creation,

Proceeding from the heat-oppressed brain?

Macbeth admits that the dagger seems as real to him as the one he holds in his hand as he goes to Duncan's chamber—almost leading him—looking just like the weapon Macbeth intends to use.

I see thee yet, in form as palpable

As this which now I draw.

Thou marshall'st me the way that I was going, (50)

And such an instrument I was to use.

Macbeth imagines that his eyes are tricking him, or they are sharper than all of his other senses put together. As he watches the dagger, he notes that where it was clean before, now it is covered in blood, as if the deed were already done. He seems to mentally shake his brain to clear it, saying, "there's no such thing." He says the cause of the vision is the evil deed he is about to carry out—it's making him see things.

Mine eyes are made the fools o’ the other senses,

Or else worth all the rest. I see thee still,

And on thy blade and dudgeon gouts of blood,

Which was not so before. There's no such thing: (55)

It is the bloody business which informs

Thus to mine eyes.

Macbeth begins to take note of the time: it is "the witching hour," when half of the world is in darkness, sleeping—but a time when wicked dreams haunt those who sleep, witches are practicing their craft, murder takes place while the wolf howls an alarm.

Now o'er the one half-world

Nature seems dead, and wicked dreams abuse

The curtain'd sleep; witchcraft celebrates

Pale Hecate's offerings; and wither'd Murder, (60)

Alarum'd by his sentinel, the wolf,

Whose howls his watch...

Now Macbeth compares himself to Tarquin, a Roman king, with whom Macbeth has much in common. Both commit their sins at night—the wolf howls, and each is frightened by what he is doing. Then Macbeth personifies the earth, asking that it not "hear" his steps for they might cry out in light of his intent. For while Macbeth "threatens," Duncan lives. The signal bell rings and Macbeth hopes Duncan does not hear it—it is the King's death knell.

...thus with his stealthy pace

With Tarquin's ravishing strides, towards his design

Moves like a ghost. Thou sure and firm-set earth,

Hear not my steps, which way they walk, for fear (65)

Thy very stones prate of my whereabout,

And take the present horror from the time,

Which now suits with it. Whiles I threat, he lives;

Words to the heat of deeds too cold breath gives. A bell rings.

I go, and it is done: the bell invites me. (70)

Hear it not, Duncan, for it is a knell

That summons thee to heaven, or to hell.

In Shakespeare' Macbeth, Lady Macbeth also delivers a soliloquy that allows us to look deep into the heart of the woman who drives Macbeth to murder Duncan—his King, his friend, his cousin, and his houseguest (a terrible act in those days).

Lady Macbeth notes the presence of a raven, a bird associated with death, as it "croaks" Duncan's approach, which Lady Macbeth has already decided will be his last entrance, to her castle. Here she calls on the dark spirits to change her so that she may be as hard and vicious as necessary to do what must be done to kill the King. She wants to no longer have the characteristics of a woman ("unsex me here") and make her capable of great cruelty, something that does not (according to Shakespeare) come naturally to a woman (the "gentler" sex). She asks that her blood be thickened, and the passage to conscience and remorse within her be blocked so she feels no guilt, so nothing stands between her and what she intends to do.

The raven himself is hoarse

That croaks the fatal entrance of Duncan (40)

Under my battlements. Come, you spirits

That tend on mortal thoughts, unsex me here

And fill me, from the crown to the toe, top-full

Of direst cruelty! Make thick my blood,

Stop up the access and passage to remorse,(45)

That no compunctious visitings of nature

Shake my fell purpose nor keep peace between

The effect and it!

She then asks the spirits of darkness ("murdering ministers") that lend strength to "human mischief" to make her mother's milk, something associated with love and nurturing of a child, be made poisonous ("gall").

Come to my woman's breasts,

And take my milk for gall, you murdering ministers,

Wherever in your sightless substances (50)

You wait on nature's mischief!

Next, Lady Macbeth addresses the cover of night, asking it to bring the dark mists of hell around her so that (personifying her weapon) her knife does not "see" the wound it intends to make in the good, "God-chosen" King; to make it dark enough that even heaven cannot see what she intends to do to and (personification again) "cry out" that she "Stop!"

Come, thick night,

And pall thee in the dunnest smoke of hell,

That my keen knife see not the wound it makes,

Nor heaven peep through the blanket of the dark

To cry, “Hold, hold!”(55)

At this point Macbeth enters, and Lady Macbeth repeats the predictions listed in his letter to her; she speaks of her joy. She will now begin to poison his mind so that he will not balk at what must be done, not only so he can be King, but that she can become Queen.

In contrast to her husband who lacks will, Lady Macbeth delivers herself as pure will in her soliloquy of Act I, Scene V.  In her first soliloquy of this scene, Lady Macbeth fears that her husband's nature is too full of the "milk of human kindness" and he is "without ambition."  Therefore, she determines that she will tempt Macbeth with unsanctified violence by her sheer force of will: 

  Shake my fell purpose nor keep peace between
The effect and it! Come to my woman's breasts,
And take my milk for gall, you murdering ministers,
Wherever in your sightless substances. (1.5.47-50)

And this force of will assumes a sexual nature as she bids the spirits to unsex her as a female, rendering her more masculine, for there is a connection in Macbeth between masculinity and violence. As evidence that masculinity and courage and violence are associated, in Scene 7, when Macbeth is told her purposes, he praises her daring and mettle by telling her,

Bring forth men-children only,
For thy undaunted mettle should compose
Nothing but males.  (1.7.81-83)

Thus, in her soliloquy Lady Macbeth determines to persuade her husband to commit murder as it becomes their mode of sexual expression. Unable to beget children, Lady Macbeth unsexes herself in order to provide her husband with the ambition and will that he lacks.  This sexual expression also has some of the Oedipal about it, as well, with Lady Macbeth's two allusions to milk.  Since Lady Macbeth asks that her breasts be rid of milk and filled with gall, the implication of motherhood is certainly suggested.  She dominates and directs Macbeth, persuading him to his self-abandonment more as a mother than a wife.  Macbeth's telling her to have male children also suggests a motherhood separate from him as he has not produced any heirs yet.

Yet she collapses while he grows ever more frightening and becomes the nothing he projects