What is the difference between an oxymoron and a metaphor?

An oxymoron is a figure of speech that combines contradictory terms to create a unique expression, such as "bittersweet" or "deafening silence." In contrast, a metaphor is a figure of speech that makes a direct comparison between two unrelated things, suggesting that one is the other to highlight similarities, like saying "time is a thief." While both enhance language and convey deeper meanings, their structures and purposes differ significantly.