Poetic Language Features

Metonymy: substituting the name of a feature for the name of a thing.
E.g: We will swear loyalty to the crown. ('Crown' in place of a royal person.)
E.g: You have all of my heart. ('Heart' in place of love or emotion.)

Irony: incongruity between what might be expected and what occurs.
E.g: Saying something is as clear as mud.
E.g: Saying "Oh, fantastic!" in a poor situation.

Synecdoche: Using part of something to refer to the whole thing.
E.g: Saying 'wheels' when referring to a car.
E.g: Referring to champagne as bubbly.