Well, don't forget Forest Gump's simile: Life is like a box of chocolates; you never know what you're going to get.
Metaphor is when you say something *is* something else. Simile uses the word "like."
Life is a crap shoot (metaphor)
Life is like a box of chocolates (simile)
Can your son make up his own? Or does he have to use well known ones like the ones I mentioned?
-Dorothy (LadyZolt)