What is the difference between a simile and a metaphor?

A simile makes a comparison explicit with like or as: her voice was like gravel. A metaphor asserts the comparison as identity: her voice was gravel. Both are figures of speech doing the same work, mapping qualities from one thing onto another, and the difference is purely in how directly the comparison is stated. Metaphor is generally the stronger device because it collapses the distance, forcing the reader to hold both images at once, while simile keeps a small analytical gap that can be useful when precision matters more than force.

Two related terms often get folded in. An analogy is an extended comparison used to explain, typically longer and more structural than either. Personification gives human qualities to nonhuman things, the wind complained, and is a specific type of metaphor. Note also that most everyday language is quietly metaphorical without anyone noticing, we grasp ideas, prices climb, arguments are attacked and defended, and linguists George Lakoff and Mark Johnson argued influentially that these conceptual metaphors structure how we actually think rather than merely decorating how we speak. The practical writing advice: mixed metaphors are the common failure, since combining two incompatible images in one sentence produces unintentional comedy, and a dead metaphor that has become cliché usually does less work than plain description.