Macbeth's reaction to being named Thane of Cawdor takes the form of a metaphor: "Why do you dress me / In borrowed robes?" Explain this metaphor. Please provide more examples and explanations of how the clothes metaphor is used elsewhere in the play.
When Macbeth learns that Duncan has named him Thane of Cawdor, he compares the new title, via metaphor, to "borrowed robes," thinking that the title cannot be his because he knows the old Thane to be alive. In this same scene, while Macbeth is considering what this new title means as far as the other prophecy he received, Banquo says, "New honors come upon him, / Like our strange garments, cleave not to their mold, / But with the aid of use" (1.3.160-162). He means that the new title sits on Macbeth like new clothes that don't quite fit well until one wears them a while.
Clothing is again used as a metaphor when Macbeth tells his wife that he doesn't want to go through with the murder. He says, "He hath honored me of late, and I have bought / Golden opinions from all sorts of people, / Which would be worn now in their newest gloss, / Not cast aside so soon" (1.7.35-38). Again, he compares the new honors he's received to clothing and says that he wants to enjoy them instead of casting them off almost as soon as he's received them. In response, Lady Macbeth uses clothing as a metaphor for hope, saying, "Was the hope drunk / Wherein you dressed yourself?" (1.7.39-40). She wonders if the hope Macbeth "wore" earlier, when they planned the murder, was a result of his drunkenness only and not his courage.
After the murder and its immediate fallout, Macduff says to Ross, "Adieu, / Lest our old robes sit easier than our new!" (2.4.52-53). He worries that their positions will be less comfortable or even less secure now, under Macbeth's rule, than they were under Duncan's.
A metaphor compares two unlike things without using "like" or "as."
So, the metaphor in Macbeth's question,"Why do you dress me / In borrowed robes?" is the Thane of Cawdor's title. A "robe" is a symbol of royalty and authority, like the title of a thane. And the word "borrowed" reveals that Macbeth does not know that the Thane of Cawdor is a traitor and who has been stripped of his title by King Duncan, and soon will be executed. Macbeth believes that the Thane of Cawdor still lives, so it comes as a complete surprise to Macbeth.