Explanation: A preposition is is a part of speech that's shows a relationship between words or a element. While a metaphor is a phrase that is applied to a noun or action to express figure of speech that isn't possible with the object or action. So with these two definition we can say that preposition is being used metaphorically when it is showing the connecting or possibly a actual interpretation. For example: John's hopes were rising, Darkness was coming over him.
