The bible as I understand it is Biblegod's 'Manual For Living'. Why does it need metaphors? This seems to only complicate things resulting in some Christians taking a literal view of Genesis for example and some thinking it is metaphorical.
Aircraft engineering manuals do not use metaphors because that would leave the way open for 'interpretation' and consequently smoking holes in farmer's fields. I'm not aware of medical textbooks using metaphor. Examples yes, metaphor no.
So Christians, please state an instance in the bible where a clear instruction or fact could be improved upon by removing the clear instruction or fact and replacing it with metaphor. Feel free to quote biblical metaphors where a clear cut instruction or fact would not suffice.