There is a difference, but seriously they are vague concepts so yeah.
The key is that metaphors are describing tools and usually refer to language, how something is described in language its about wordsssss
Okay I'm stuck but say if I was describing the car like a knight in shining armour
Symbolism is more about themes and deeper meanings
ie
at a climax say a cross falls off the top of the church. This would symbolise religious defeat. The cross is symbolic of religion.
but yes its iffy, the word visual metaphors isn't used that much (at least not at my school,) if you can't choose between what word, use symbolism, its just more recognisable to the markers.