Very gorgeous picture. I love the way you've done the robe. The beautiful golden hair and the how the gold is in the robe like water. It's beautiful when combined with the background as well.
However, in the Silmarillion it's noted that Melkor has always been the darkness where Manwe was light. When Illuvatar created the Valar to sing their songs and essentially create Arda, Melkor's song was always known to be one of chaos that ultimately disrupted the others'.
His name Morgoth was only given to him by Feanor as it meant "Dark Enemy" after slaying his father and the elves called him that afterward.