Michael originally served in the lower ranks of the First House as the Cherub of the Unerring Beam. Then, Lucifer, the Morningstar and first among the Heralds, decided to side with the rebellious angels who wished to make humanity aware of the potential they had. After Lucifer defected, Michael was promoted by God and given the flaming sword and position as the head of the First House. He was sent to Eden with an offer for the rebels: surrender and simply be unmade. Out of over thirty-million Elohim, only two returned for this punishment; Amiel and Ank-Rhuhi.
The first battle in the Age of Wrath was between Lucifer and Michael; the latter had not learned the extent of his new powers and weapon, and was reluctant to strike his former leader. As a result, Lucifer won the first battle of the Age of Wrath, clearing the way for the rebellious angels and humans to work together. One quarter of humanity, however, decided to follow the will of God, and Michael took them from the rest.
Since they refused the original punishment of ceasing to exist; God created a punishment for each of the Houses and sent Michael forth to name the rebellous Elohim, now called the Fallen, and give each House their punishment. Michael also led the final charge in the War of Heaven at Genhinnom that resulted in Heaven's victory and the banishment of the Fallen to the Abyss.
When Caine was "Awakened" by drinking Lilith's blood in the Land of Nod, it was Michael who first appeared to Caine and offered him redemption. When Caine refused, Michael cursed him and his descendants to be forever burned by fire.