Melkor visste att männen så småningom skulle uppstå
In those days, moreover, though the Valar knew indeed of the coming of Men that were to be, the Elves as yet naught of it; for Manwë had not revealed it to them. But Melkor spoke to them in secret of Mortal Men, seeing how the silence of the Valar might be twisted to evil. Little he knew yet concerning Men, for engrossed with his own thought in the Music he had paid small heed to the Third Theme of Ilúvatar; but now the whisper went among the Elves that Manwë held them captive, so that Men might come and supplant them in the kingdoms of Middle-earth, for the Valar saw that they might more easily sway this short-lived and weaker race, defrauding the Elves of the inheritance of Ilúvatar.
—The Silmarillion
Även om han inte var så kunnig som den andra Valaren, och föredrog att spendera sin tid på att trotsa Eru snarare än att lyssna på musiken, visste han fortfarande att människor skulle komma till slut.
Valaren trodde säkert att Morgoth kunde söka människor:These things the Valar did, recalling in their twilight the darkness of the lands of Arda; and they resolved now to illumine Middle-earth and with light to hinder the deeds of Melkor. For they remembered the Avari that remained by the waters of their awakening, and they did not utterly forsake the Noldor in exile; and Manwë knew also that the hour of the coming of Men was drawn nigh. And it is said indeed that, even as the Valar made war upon Melkor for the sake of the Quendi, so now for that time they forbore for the sake of the Hildor, the Aftercomers, the younger Children of Ilúvatar.
—The Silmarillion
Och hur kunde Melkor kommunicera med män?
Melkor kunde röra andras sinnen
Som framgår av @Ber, hade Melkor, liksom alla Vala, en stor förmåga att kommunicera sinne till sinne och avgörande för att veta vad andra tänkte.
Genom detta kunde han lära sig män, älvar eller vad som helst, så länge de inte var försiktiga med honom.For he would come by stealth to a mind open and unwary, hoping to learn some part of its thought before it closed, and still more to implant in it his own thought, to deceive it and win it to his friendship.
—Osanwë-kenta
Melkor kan ha lärt sig sitt språk, eller lärde dem sina egna
Han var också känd av Valar för att ha en bra facilitet med språk, så var hans önskan att använda den för att undergräva andras motstånd för att rikta sin viljans tillämpning."From the first he was greatly interested in 'language,' that talent which the Eruhini would have by nature; but we did not at once perceive the malice in this interest, for many of us shared it, and Aule above all. But in time we discovered that he had made a language for those who served him, and he has learned our tongue with ease. He has great skill in this matter. Beyond doubt he will master all tongues, even the fair speech of the Eldar. Therefore, if ever you should speak with him, beware!"
—Osanwë-kenta
Detta föreslår att Melkor kunde ha förvärvat det språk som de tidiga människorna kan ha haft, särskilt med tanke på att de i början inte var försiktiga.
Det är faktiskt möjligt att han lärde vissa människor sitt eget språk, vilket framgår av föregående text, vilket både skulle underlätta kommunikationen och göra det lättare att forma dem till hans syfte.