Idk about the bible exactly but he's in the Abrahamic religions in general, he's mainly mentioned in the Jewish books, apocryphal, rabbinic, and kabbalistic texts and talmud, but absent in Quran and the bible, but yeah he's an actual character in these religions
Im didnt learn anything from theology but is Metatron really in the bible, in Dear Door they introduce Metatron too, didnt know he was known