Simple Definition:

Metaphor is a figure of speech used to compare two things that are not alike, by saying that one thing is the other. It is a way of describing something by using words that are not meant to be taken literally. For example, saying “Her smile is a ray of sunshine” means that her smile brings warmth and brightness, like the sun.

Very Simple Definition:

Metaphor is a way of saying one thing is another thing, even though they are different. It is like using words to paint a picture in your mind. For example, saying “He is a lion on the soccer field” means he is strong and fierce, like a lion.