Metaphor

Definition: a type of figurative language in which you compare two things

Example: The fog comes in on little cat feet.
                It sits looking over the harbor and city
               on silent haunches
               and then, moves on. - 'Fog' - Carl Sandburg.
           
 In this extended metaphor the fog is being compared to a cat.

Explanation: Metaphors are important to poetry because they can add pizzazz to your work. Instead of being too literal with the meaning, you can compare it to something else. It gets the reader more involved in the writing when they have to interpret what the meaning is.