In the Valaquenta thus it is said:
“Aulë has might little less than Ulmo. His lordship is over all the substances of which Arda is made. In the beginning he wrought much in fellowship with Manwë and Ulmo; and the fashioning of all lands was his labour. He is a smith and a master of all crafts, and he delights in works of skill, however small, as much as in the mighty building of old. His are the gems that lie deep in the Earth and the gold that is fair in the hand, no less than the walls of the mountains and the basins of the sea. The Noldor learned most of him, and he was ever their friend. Melkor was jealous of him, for Aulë was most like himself in thought and in powers; and there was long strife between them, in which Melkor ever marred or undid the works of Aulë, and Aulë grew weary in repairing the tumults and disorders of Melkor. Both, also, desired to make things of their own that should be new and unthought of by others, and delighted in the praise of their skill. But Aulë remained faithful to Eru and submitted all that he did to his will; and he did not envy the works of others, but sought and gave counsel. Whereas Melkor spent his spirit in envy and hate, until at last he could make nothing save mockery of the thought of others, and all their works he destroyed if he could.”
It is also interesting to note that Melkor’s chief lieutenant: Sauron, was originally of the Maia of Aulë and Saruman was also a Maia of Aulë. The Noldor got into a lot of trouble later on and so did the dwarves (which were created by Aulë).
Because Melkor did not submit his things before Eru and was malicious towards his peers, he became weakened. Middle-earth became his ring (Morgoth’s Ring), and he was ever bound to it because of all of his will that was poured into it. Therefore towards the end of his dominion, he came forth seldom and depended on his servants, for he no longer had the strength to do such things as were done. He gave it all unto them. This made Sauron much worse than he, because Sauron was not drained, he just ruled what Melkor had wrought.