Final answer:
Macduff's warning through the clothing metaphor cautions against assuming unnatural positions or roles, revealing the discomfort and potential peril of such an action. It suggests that one should be wary of ill-fitting roles, as in the metaphor of wearing new and uncomfortable clothing.
Step-by-step explanation:
The warning Macduff gives through the clothing metaphor in Shakespeare's Macbeth revolves around the caution against assuming powers or positions that do not fit one's true nature or abilities, which can lead to disastrous consequences.
For example, when Macduff sends farewell to Malcolm, he says, 'Well, may you see things well done there: adieu! Lest our old robes sit easier than our new!' This metaphor suggests the discomfort and potential danger of finding oneself in a new, unfamiliar role that one may not be ready or suited for, much like wearing new, ill-fitting clothes compared to comfortable old robes.
Another instance is when Macbeth wonders why he is being dressed in 'borrow'd robes' after hearing that he is to become the Thane of Cawdor, revealing his initial discomfort with the sudden elevation in status and the unearned honors that come with it.