If the Bible is metaphorical then perhaps so is the God of the Bible

We should note that there is no-one who takes every part of the Bible literally.Then general rule would seem to be: when you come across something you know to be untrue, decide that it was meant to be a metaphor. You can, of course, reduce the frequency with which you're obliged to do this by knowing as little as possible.

But they don't. Comparison of statements in the Bible with reality.

I did not say that the things people take literally are things that they have compared with reality and found to be correct, I said that the things people take metaphorically are things that they have compared with reality and found to be incorrect.

Well, no it isn't. Because there are certain statements in the Bible (most of them, I should say) with which there is nothing external to the Bible to compare them. The proposition that (for example) Jacob had twelve sons, cannot be compared with any evidence external to the Bible to test it, and can therefore be taken literally rather than metaphorically. As I've suggested, by default: they think it's true except where they have to think otherwise.