Now in his heart Melkor most hated the Eldar, both because they were fair and joyful and because in them he saw the reason for the arising of the Valar, and his own downfall. Therefore all the more did he feign love for them and seek their friendship, and he offered them the service of his lore andlabour in any great deed that they would do. ... The Noldor took delight in the hidden knowledge that he could reveal to them; and some hearkened to words that it would have been better for them never to have heard... ...
For Feanor ... was filled with a new thought, or it may be that some shadow of foreknowledge came to him of the doom that grew near, and he pondered how the light of the Trees ... might be preserved imperishable. Then he began a long and secret labour, and he summoned all his lore, and his power and his subtle skill; and at the end of all he made the Silmarils. ... All who dwelt in Aman were filled with wonder and delight at the work of Feanor. ... The heart of Feanor was fast bound to these things that he himself had made....
Then Melkor lusted for the Silmarils, and the very memory of their radience was a gnawing fire in his heart. ... Long was he at work, and slow at first and barren was his labour. But he that sows lies in the end shall not lack of a harvest, and soon he may rest from toil indeed while others reap and sow in his stead. Ever Melkor found some ears that would heed him, and some tounges that would enlarge what they had heard; and his lies passed from friend to friend, as secrets of which the knowledge proves the teller wise. Bitterly did the Noldor atone for the folly of their open ears in the days that followed after.
Thus ere the Valar were aware, the peace of Valinor was poisoned. The Noldor began to murmur against them, and many became filled with pride, forgetting how much of what they had and knew came to them in gift from the Valar. Fiercest burned the new flame of desire for freedom and wider realms in the eager heart of Feanor; and Melkor laughed in his secrecy, for to that mark his lies had been addressed, hating Feanor above all, and lusting ever for the Silmarils.
And when Melkor saw that these lies were smouldering, and that pride and anger were awake among the Noldor, he spoke to them concerning weapons; and in that time the Noldor began the smithying of swords... Shields also they made displaying the tokens of many houses and kindreds that vied one with another... and Feanor made a secret forge, of which not even Melkor was aware; and there he tempered fell swords for himself and for his sons.
Thus with lies and evil whisperings and false counsel Melkor kindled the hearts of the Noldor to strife; and of their quarrels came at length the end of the high days of Valinor and the evening of its ancient glory.
The story continues on. Through Melkor's intrigue Feanor draws his sword against his half-brother, Elrond's ancestor, and is cast out by the Valar. Eventually Melkor does steal the Silmarils and Feanor swears a ruinous oath to reclaim them. The greed and strife he introduced eventually leads elf to battle elf and a large portion of the elves are sent into exile in Middle-earth. We read that the elves of the Third Age are "sorrowful" and it would be a reasonable argument that this is a direct result of their delight in "hidden knowledge."