The entire Bible reports it as history - from Moses to David; from Solomon to Ezekiel; from Jesus to the last living disciple of Jesus.
There are parts which are history. There are parts which are poetry. There are parts which are mythological. There are parts which are allegorical. And so forth. As Subduction Zone pointed out already, why is it viewed with such an all-or-nothing approach? That wouldn't be wise. It's an easy way for one to lose faith when they set it up like that. All it takes is one error of fact and the whole thing collapses under such an artificial constraint.
If you look at any culture's origin myths, they read as history too. Mythologies do this. Gone with the Wind writes about America's Civil War, but the stories woven into that are fictional. Just because the Civil War happened, does not make the story actual history. And because it's not actual history, this does not therefore mean the story is crap, unless you need it to be factual first before it has meaning. That I consider to be a problem with the
reader, not the literature. Same thing with the Bible.
It is not written metaphysically, and God himself - in relating it - says that it is history.
Of course the Bible deals with metaphysics! Metaphysics deals with the origin of things, beyond physics in other words. In fact most of what it deals with are metaphysical questions in nature.
If you want, I can make a list of all the scriptures that show this.
No need to. I've studied and read the Bible from cover to cover. Have you ever read the entire thing yourself?
If Genesis is not history, then all the characters right down to the apostle John, are mythical, and all the books too.
I am honestly not sure how you can leap from Adam and Eve being mythological characters to John being mythological. One does not follow through to the other. Each has to be looked at on its own.
I am guessing that you are needing to think in these all-or-nothing terms is because of some artificial construct you have superimposed upon the whole thing. I believe that is probably the artificial construct of the "Biblical Inerrancy Doctrine". That is a very
modern doctrine, and not one that Christianity as a whole believed in previously. Not all Christians need the Bible to be believed in that way in order for their faith to be real. I consider tying one's faith to the modernistic Inerrancy Doctrine to be at odds with actual Faith.
If one loses faith in God because they found out there are errors in scripture, then I would say that faith was one built on a bed of shifting sand. It is faith built as a house of cards where one little tremor can topple the whole thing. Denialism about things like science and history because it runs into one's beliefs about the Bible, is a trainwreck of faith just waiting to happen.
What reason do you have for saying it's metaphorical?
I could easily write a whole book on this. In brief however, a metaphor points to something beyond itself as the thing to be considered. For instance, when you look at the night sky it is strewn with countless stars in a jumble of dots littering your field of vision. But if you draw a line from one point of light to another, and to another, and another, you impose a pattern upon it which the mind can recognize and relate to it.
This is what the constellations are. Orion is not actually up there in the sky, right along with Leo, or Scorpio, or the Big and Little Dippers. Those are metaphorical figures we use to try to relate to the transcendent.
Many of the figures of the Bible, the characters of Adam and Eve for instance, are images of humanity as a whole dealing with things like our human natures, sin and temptation, guilts, shames, regrets, pain and suffering, etc. Everyone can relate to this on some level or another. This is what good mythologies do. This is what they are for. Relatability. They are usually timeless truths that transcend cultures.
The myth of the Garden and the Fall of man is a story about us. To reduce it down to "historical fact" guts it of that. If it can't be "true" in a timeless sense, beyond historical facts, then it is a worthless story. It doesn't capture the imagination. It gets rid of imagination reducing it to a simple fact-finding task. It is imagining that is the wings of faith. Without that there, faith is dead.