Macbeth's Face
Lady Macbeth cautions Macbeth against showing his every emotion, and encourages him to be more stoic so as to conceal his inner thoughts. She tells him, "Your face, my thane, is as a book where men / May read strange matters," using a simile to suggest that Macbeth's face is easily readable by others (1.5).
Appearance
Following her accusation that Macbeth does not conceal his anguish well enough, Lady Macbeth encourages him to "Look like th' innocent flower, / But be the serpent under ’t" (1.5). In this metaphor, Lady Macbeth is telling her husband to appear benevolent while secretly maintaining his hidden agenda of murdering Duncan.
Duncan's Death
After Macbeth murders Duncan, he is tasked with telling Malcom and Donalbain that their father has died. He says, "The spring, the head, the fountain of your blood / Is stopped; the very source of it is stopped" (2.3). In this metaphor, Macbeth compares Duncan to the origin of the boys' own lives, showcasing the play's interest, once again, in patrilineal inheritance.
Banquo and Fleance
Once Macbeth learns that Banquo's sons are to inherit the crown, he becomes anxious about Banquo and his young son, Fleance. Seeing them, he says to himself, "There the grown serpent lies. The worm that’s fled / Hath nature that in time will venom breed; / No teeth for th’ present" (3.4). In this metaphor, Macbeth compares Banquo to a snake who threatens his power, while also comparing Fleance to a young serpent who will eventually also pose a threat. These thoughts are what lead Macbeth to order the murder of Banquo and his son.
Macduff's Grief
After learning of the murder of his wife and children, Macduff laments, "All my pretty ones? / Did you say all? O hell-kite! All? / What, all my pretty chickens and their dam / At one fell swoop?" (4.3). In this metaphor, Macduff affectionately refers to this wife and children as a family of chickens while also comparing Macbeth to a murderous kite, or bird of prey.