Metaphor is a figurative expression.

Metaphor compares two different things in a figurative sense. Unlike in a simile (A is like B.), "like" is not used in metaphor (A is B.).

Example:

Truths are first clouds, then rain, then harvest and food. (Henry Ward Beecher)

Through much of the last century, America's faith in freedom and democracy was a rock in a raging sea. Now it is a seed upon the wind, taking root in many nations.