A simile is a way of describing something by comparing it to something else.
He rushed in and out again like a whirlwind.
I can easily lift this case. It's as light as a feather
A simile uses the words 'like' or 'as....as'.
Metaphors also compare things, but do not use the words 'like' or 'as....as'. When we write metaphors we state that something actually is something else, even though it is impossible.
My feet are blocks of ice.
Our feet are not really blocks of ice, but using this metaphor is more interesting than simply saying 'my feet are cold'.