The Valar were sort of like angels, and there were 13 of them, withMorgoth being the second most powerful. He wanted dominion over the others and over the ages turned against his felow Valar. The Silmarilion, goes into detail about the endless wars Morgoth waged against his former brethern. The Maiar were powerful spritits, that served the Valar, Morgoth corrupted some of those, Sauron was one of those as were the Balrog that Gandalf fought in the Fellowship of the Ring in Moria. I suspect Saruman, Radagast and the Blue Wizards were Maiar as well, although of the 5, only Gandalf completed his mission.