In Act 1, Scene 2, the importance of honor emerges as a theme. Macbeth is hailed as a noble warrior, and Duncan bestows an additional title of honor on him: Thane of Cawdor. The current Thane of Cawdor has proven to be a traitor and will be executed. Disloyalty is not tolerated and the king values men who stand loyal to the crown. This theme will ironically run through the play as Duncan has been greatly mistaken to trust Macbeth's sense of honor and loyalty.

In Act 1, Scene 5 and again in Scene 7, another theme emerges: the stereotypical influences of gender roles. After reading Macbeth's letter in Scene 5, Lady Macbeth begs for the power to overcome her traditionally weaker femininity:

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. (I.v.45-48)

Lady Macbeth wishes to be "unsexed," or to have her femininity removed from her so that she can instead be filled with cruelty. She goes on to beg that feelings of regret be blocked from her so that she can help her husband accomplish his greatest ambitions.

Later in Scene 7, she plays on Macbeth's fears of not being viewed as masculine in order to sway his thoughts:

What beast was ’t, then,
That made you break this enterprise to me?
When you durst do it, then you were a man;
And to be more than what you were, you would
Be so much more the man. (I.vii.52-56)

If he wants to be a man, he will do as his wife commands (which is pretty ironic in itself). She even summons up startlingly violent images which break from expected maternal roles to further show her own strength as a woman:

How tender ’tis to love the babe that milks me.
I would, while it was smiling in my face,
Have plucked my nipple from his boneless gums
And dashed the brains out, had I so sworn as you
Have done to this. (I.vii.60-64)

Certainly this is done to make clear to Macbeth that she is not a member of the weaker sex and that he therefore needs to prove his own strength by being equally willing to commit violent acts. This is another theme which will carry through the play with some interesting contrasts in the expectations of masculinity noted between Macbeth and Macduff.

In Act I, Shakespeare introduces a number of key themes. Firstly, through the witches, he introduces the theme of the supernatural. This is important because it sets the tone for the rest of the play. The use of magic, for instance, creates a mysterious feel for the reader.

The line "Fair is foul, and foul is fair" adds to this supernatural feel and also introduces another key theme—deception. So, right from Act I, the reader is prepared to understand that not everything is quite as it seems in this story. This theme is also important in Scenes 6 and 7 when Macbeth is preparing to murder King Duncan.

Finally, the theme of loyalty is also significant in the first Act. As we see from the descriptions of Macbeth on the battlefield, he appears to be an extremely loyal and dedicated servant of King Duncan. But, as the act unfolds, we realize that his loyalty is questionable. Again, this feeds into the theme of deception and also establishes the theme of ambition.

Here are the main themes with supporting quotes from Act I of Macbeth:

• Ambition can subvert reason

“Thou wouldst be great; art not without ambition, but without the illness should attend it.”–Act I, Scene 5

• When supernatural powers represent evil, they should be ignored.

“But ‘tis strange! And oftentimes, to win us to our harm, the instruments of darkness tell us truths, win us with honest trifles, to betray’s in deepest consequence.”–Act I, Scene 3

• Appearances do not always reflect reality.

“There’s no art to find the mind’s construction in the face. He was a gentleman on whom I built an absolute trust.”–Act I, Scene 4

• Despite prophecies of the future, people are responsible for their own actions.

“If you can look into the seeds of time and say which grain will grow and which will not, speak then to me, who neither beg nor fear your favors nor your hate.”–Act I, Scene 3