In the same manner that Lady Macbeth goads her husband on to murder, Macbeth provokes the murderers he hires to kill Banquo by questioning their manhood.
Toward the end of the play he descends into a kind of frantic, boastful madness.
Lady Macbeth, on the other hand, pursues her goals with greater determination, yet she is less capable of withstanding the repercussions of her immoral acts.
In the scene where Macduff learns of the murders of his wife and child, Malcolm consoles him by encouraging him to take the news in “manly” fashion, by seeking revenge upon Macbeth.
Macduff shows the young heir apparent that he has a mistaken understanding of masculinity.
In the play, Duncan is always referred to as a “king,” while Macbeth soon becomes known as the “tyrant.” The difference between the two types of rulers seems to be expressed in a conversation that occurs in Act 4, scene 3, when Macduff meets Malcolm in England.
In order to test Macduff’s loyalty to Scotland, Malcolm pretends that he would make an even worse king than Macbeth.
To Malcolm’s suggestion, “Dispute it like a man,” Macduff replies, “I shall do so. At the end of the play, Siward receives news of his son’s death rather complacently.
Malcolm responds: “He’s worth more sorrow [than you have expressed] / And that I’ll spend for him” (5.11.16–17).
This is proven several times throughout the course of the play; through Lady's Macbeth provoking Macbeth to kill by doubting his manhood, through Macbeth questioning the manhood of the hired murderers in order to convince them to kill Banquo, and through Malcolm telling Macduff to seek revenge in a manly fashion after his family has been murdered.
The main theme of Macbeth—the destruction wrought when ambition goes unchecked by moral constraints—finds its most powerful expression in the play’s two main characters.