What is a metaphor?

A metaphor is a figure of speech which refers to one thing by mentioning another thing. Some examples of metaphor are as follows: If you wanted to say that a person is angry, you can say that “He/She is boiling mad.” If you wanted to say that the exam was easy, you can say “the exam was a breeze.” Metaphors are commonly used in literature such as in William Shakespeare’s Shall I Compare Thee to a Summer’s Day when he used the words “But thy eternal summer shall not fade…”, in John Keats’ When I Have Fears when he used the words “Before high-pil’d books, in charact’ry hold like rich garners the full-ripened grain,” and in Kate Chopin’s The Storm wherein she mentioned “Her mouth was a fountain of delight.”