Metatron never appears in the Hebrew Bible. He surfaces in Talmudic passages and fully in 3 Enoch, the Hekhalot text where the human Enoch is taken up, enlarged, given 72 wings and 365,000 eyes, enthroned beside the glory, and renamed YHWH ha-qatan, the Lesser YHWH, because, per Exodus 23:21, my name is in him. He becomes heaven's scribe and vice-regent, the one being permitted to sit in God's presence.
The Babylonian Talmud tells the cautionary tale: Elisha ben Avuyah ascends, sees Metatron seated, and concludes there are two powers in heaven, heresy. Metatron is punished with sixty fiery lashes to teach him, and everyone watching, that even the greatest angel stands when God is present. Peter Schäfer reads the whole cycle as the rabbis defusing a binitarian theology that had taken root in mystical circles, a second God, demoted by flogging.
The claim: Metatron preserves the memory of Israel's older divine council, the second power, the angel of the name from Exodus, the son of man figure, and the rabbinic beatings are the scar tissue of monotheism cauterizing its own polytheistic past. Verdict: Schäfer's Two Gods in Heaven argues a version of this seriously, and the Exodus 23 basis is real. But scar tissue is not the wound: what the pre-monotheistic structure actually was remains reconstruction, elegant, documented at the seams, unprovable at the core.
What do you do with an angel who shares God's own name?