Can you explain the difference between a simile and a metaphor?

Similes and metaphors are both methods of comparing something, in order to describe it in a more imaginative way. With a metaphor, you are simply stating a comparison, e.g.: her eyes were emeralds. Her eyes aren't actually emeralds, but the metaphor here adds a sense of beauty to the image. On the other hand, similes use "like" or "as" for comparison. So, in the case of the simile above, if it were a metaphor we would say: "her eyes were like emeralds". They are both examples of imagery, and though they are different, they essentially serve the same purpose.