What is a metaphor?

A metaphor is indeed a figure of speech that makes a comparison without using 'like' or 'as.' This type of figurative language draws a direct relationship between two unlike things, suggesting that one is the other in some way. For example, saying "Time is a thief" implies that time takes away moments from our lives just as a thief takes away possessions, evoking a deeper understanding and emotional response.

Using a metaphor allows writers to create vivid imagery and convey complex ideas in a more relatable manner. It enriches the text by providing deeper layers of meaning and engaging the reader’s imagination. This tool is prevalent in poetry and prose, illustrating an idea or emotion in a more nuanced way than a straightforward description could achieve.

The other choices represent different literary devices or formats and, while they can contribute to a text's richness and complexity, they do not define a metaphor. For example, the first choice describes a simile, which specifically uses 'like' or 'as' to make a comparison. The second refers to hyperbole, which is about exaggeration, and the last defines a formal writing structure, which is unrelated to the concept of metaphor.