obvious exaggeration.

        E.g.: “He’s older than dirt!”

words that literally express a meaning that is the opposite of the intended meaning, characterized by self-reflexion; an expression meant to indicate its opposite.  Sarcasm and satire are often based on irony.

E.g., if, calling home from the arctic temperatures of January in Missouri, you say, "Oh yes, it's positively balmy here.  I don't know if I can survive such a tropical heat-wave!"

Metaphor

explicit comparison of two things, using "like" or "as."

E.g.: "O, my luve is like a red, red rose" (Robert Burns).