When god explains how to treat your slaves, it must be a metaphor. When he says to love your neighbour, it is the literal truth.
When something is particularly clear and nice in your scripture it is the literal word of god. When something is particularly obnoxious in your scripture, it is a metaphor.
How do you know which is which? The whole point of your scripture seems to be to help you make sense of the world and make the right life choices. Understanding when something is literally true or a metaphor seems pretty essential to actually using scripture as a guide for your life. Shouldn’t this guide help you in that? If you have to know by some other means – « obviousness », gut feeling, empathy, hearsay – which is which, those other means are even more important than the scripture itself.
Say you are looking for « morals » in scripture. Once it says « do not judge », then « kill the adulteress ». Which is the literal truth, if either, and which is the metaphor? It seems you would need a good sense of morality to figure out which to believe. But then, you don’t need the scripture…
Or you just believe what someone tells you – a priest, rabbi, imam, talking rabbit – and that just pushes the question to where they found the information.