Metatron, named Enoch when he was a man, was an angel and the Regent of Heaven. He became more powerful than the Authority and seized control. He took up regency to the throne in order to implant the monotheistic religions across the universes and, by doing so, he affirmed his command and rule. To keep dominance, he betrayed and trapped the Authority in the crystal box; this successfully kept the other angel alive, but imprisoned. Metatron sought to supplant God, destroy Lord Asriel and his army, and kill Lyra Belacqua. He shared the belief of many that Lyra was the second Eve, who was destined to fall into temptation like the first. In the end, Metatron was killed by Lord Asriel and Marisa Coulter as they all fell into the abyss to become ghosts for all eternity.
Metatron was once a man named Enoch (son of Jared, son of Mahalalel, son of Kenan, son of Enosh, son of Seth, son of Adam), and he was Baruch's brother.
Though he became an angel, he still had human vices, and consequently became greedy and oppressive with God's rule. This was a major weakness, as it left him vulnerable to the lecherous temptation of Marisa Coulter.