'Perhaps you consider yourself an oracle, / Mouthpiece of the dead, or of some god or other. / Thirty years now I have labored / To dredge the silt from your throat' - Sylvia Plath uses which metaphor in these lines from her poem, 'The Colossus'?

A metaphor states that one thing is something else. This description, however, is too simple for the way metaphors often work in poetry, literature and speeches. You will often find something being described, or written about, as if it is something else, without the writer ever saying 'x is y' (do you see the mathematical metaphor there?).