Melkor never intended to steal the Silmaril's and start the war that devastated Beleriand. First he approached Feanor, expressing his desire to posses one of the magnificent jewels, and offering a trade. After some bargaining, Melkor agreed to pay for one Silmaril in sex acts, but after he had fulfilled his part of the bargain, Feanor declared that Melkor was terrible at giving head, and withheld the jewel. Only then did Melkor seek out Ungoliant to exact his revenge.