In Shakespeare's Macbeth, some of the main characters share several similarities, while others are quite unique.
Macbeth (at the beginning), Banquo and Macduff all prove themselves to be men of great courage, skill in battle and loyalty. In Act One, the Sergeant gives a report of Macbeth's skills in battle for King Duncan and Scotland:
For brave Macbeth—well he deserves that name— Disdaining fortune, with his brandish'd steel, Which smoked with bloody execution, Like valor's minion carved out his passage Till he faced the slave, Which ne'er shook hands, nor bade farewell to him, Till he unseam'd him from the nave to the chaps, And fix'd his head upon our battlements. (I.ii.18-25)
However, as the play continues, Macbeth allows himself to be wooed away from these characteristics by the witches' equivocations (lies) or doublespeak as they promise that he will not only be king, but be invincible as well.
Macbeth is not, however, an easy mark: while he is enchanted with the idea of being king, he wavers from that intent for several reasons. Duncan has recently rewarded him for his achievement in battle, and has promised to honor him still further. This shows Macbeth's sense of loyalty. It should be noted that Duncan is not only the King, but Macbeth's friend and cousin. At the time of Duncan's death, Macbeth is Duncan's host—killing one's guest was considered the highest from of betrayal. Macbeth is devoted to his wife; he is also brave even when the odds are stacked against him. It is for his wife that Macbeth finally agrees to the plan to kill Duncan. And even when Macbeth realizes that the witches have tricked him, at the play's end, he refuses to commit suicide, but fights till the death with Macduff.
Lady Macbeth, on the other hand, is a scheming and murderous woman who is also mentally unstable. When she hears that the witches have told Macbeth that he will be king, she begins to plan Duncan's death. When she discovers that Macbeth is having second thoughts, she shows the darkness of her soul when she tells her husband that should could murder her own baby, if she had promised to do so:
I have given suck, and know How tender ’tis to love the babe that milks me: I would, while it was smiling in my face, Have pluck'd my nipple from his boneless gums, And dash'd the brains out, had I so sworn as you Have done to this. (I.vii.60-65)
By the play's end, Lady Macbeth—seemingly so strong at the play's start—has lost her mind. We can assume that she was always prone to mental instability. If the audience was not certain of this when she spoke of murdering her own baby, certainly there is not doubt when (in the last act) she walks in her sleep mentally reliving aloud Duncan's murder, and later kills herself.
Banquo is a man who cannot be swayed by witches' predictions for him. He will not turn away from his duty to his king or country to protect his friend, Macbeth. When things begin to fall into place after Duncan's murder, and Macbeth has all the witches promised, Banquo becomes suspicious. Macbeth knows that Banquo will never be turned from doing the right thing—as seen when he refers [below] to Banquo's "royalty of nature." It is for this reason that he orders Banquo and Fleance's murders.
Our fears in Banquo Stick deep, and in his royalty of nature Reigns that which would be fear'd. (III.i.53-55)
Banquo and Macduff are not only loyal to Duncan, but they are also men who love their children, and are so devoted to their king that they put all they value on the line to maintain their loyalty. When Banquo and his son return from riding and the murderers attack, Banquo fights the men off, encouraging his son to flee for his life.
Macduff is devastated to see how ravaged Scotland has become under Macbeth's tyrannical rule. He is a true patriot to the point of death. Uncertain of what Malcolm's welcome will be when Macduff travels to England (where Malcolm is living—fearful that Macduff might be Macbeth's spy, sent to kill him), Macduff makes the journey without fear for himself. Perhaps foolishly, he is so devoted to Scotland that he makes no provision for the safety of his family—all who Macbeth has murdered. In this moment it is safe to infer that when his family was killed, Macduff would like to have died—for he loved them as he loves Scotland. When he returns with Malcolm to fight Macbeth, Macduff again shows his bravery, committed to fight Macbeth even if it means his death.
Duncan is a good king, loved by his subjects. Generous of nature, he rewards those who serve him valiantly. He takes pride in the loyalty of his subjects, as seen in his delight over Macbeth's prowess on the battlefield for the benefit of Duncan and Scotland. Perhaps Duncan is too trusting and not as wise as he should have been. It is impossible to have so much and believe without the whisper of doubt that no one wants to take it away. That is not to say that a great man should be paranoid or fearful all the time, but being away from his palace, one might have expected more guards to ward off an attack, especially where he was in an unfamiliar place. It need not have been Macbeth who attacked and killed him; anyone finding Duncan away from the safety of his castle could have plotted to take his life.
The witches are spiteful, deceitful and not terribly bright. The second time the audience meets the witches, one is angry because a woman would not share her chestnuts with the witch. So the witch decides to punish the woman's husband instead, and puts a curse upon him—with which all the other witches eventually agree to help.
A sailor's wife had chestnuts in her lap, And mounch'd, and mounch'd, and mounch'd. “Give me,” quoth I. “Aroint thee, witch!” the rump-fed ronyon cries. Her husband's to Aleppo gone, master o’ the Tiger; But in a sieve I'll thither sail, And, like a rat without a tail, I'll do, I'll do, and I'll do. (I.iii.4-11)
Certainly the witches are deceitful. The prophecies they give Macbeth are only half-truths. He will become king, but only if he kills Duncan. A man born of woman cannot kill him, but the witches play with the word "born," literally meaning that a man born in the way will not kill Macbeth. Macduff was delivered by Caesarian-section, and so he was not born in the way other people are born. He is able to kill Macbeth.
Hecate, the Goddess of the Witches, points out the foolishness of the witches.
Have I not reason, beldams as you are, Saucy and overbold? How did you dare To trade and traffic with Macbeth In riddles and affairs of death; And I, the mistress of your charms, The close contriver of all harms, Was never call'd to bear my part, Or show the glory of our art? And, which is worse, all you have done Hath been but for a wayward son, Spiteful and wrathful: who, as others do, Loves for his own ends, not for you. (III.v.1-13)
She scolds the women for three reasons. They never called Hecate into the fun they have had messing with Macbeth's life and fate. Secondly, they have done nothing to bring others to praise their skills with the black arts. Finally—the worst thing, says Hecate—is that they have given Macbeth things that have fed his desires, but not caused him to be devoted to them for their work.
In studying the characters—especially at its start—Macbeth, Banquo and Macduff have a great deal in common. They are family men. They are brave warriors. They are loyal to king and country. However, Macbeth allows personal ambition and his wife to pull him away from the man he is at the play's outset.
Duncan is generous and proud of his men, but perhaps he could have been wiser, more cautious. Lady Macbeth is evil from the opening, as are the witches. Like the witches, she is also a schemer. However, unlike Hecate's servants, Lady Macbeth has a flawed psyche: she loses her mind over her guilt.
It is only in studying each of these characters that we understand their motivations, their weaknesses and their failures. On the other hand, we also see men of strong character and dedication, interested in serving the greater good rather than self.