Which of the following best defines a metaphor?

A metaphor is defined as a direct comparison between two unlike things without using "like" or "as." It suggests that one thing is another, enabling a deeper understanding or insight through the association between the two. For example, saying "Time is a thief" implies that time steals moments from our lives, enhancing the emotional impact of the statement by creating a vivid image.

The other choices describe different literary devices. Exaggeration for effect refers to hyperbole, which amplifies a situation for dramatic or humorous purposes. A statement that seems contradictory but may reveal a truth characterizes an oxymoron or paradox, which challenges common perceptions to highlight complex truths. A comparison using "like" or "as" defines a simile, which, while similar to a metaphor, is distinctly different in its explicitness about the comparison.