As the Years of the Sun began, the Valar left Middle-earth to the control of Morgoth, as they were safe in Valinor, except for Ulmo, who gathered and passed news through the waters. Life, however, flourished in Middle-earth, and at the first rising of the Sun, Men awakened in Hildórien.
Because they woke in the first light of the Sun, Men tended to stray toward it, and—unlike the Elves—the Valar did not come to council and guide them. Men, then, have tended to fear the Valar, not understanding them or their purposes. Ulmo, though, again did not forsake the children of Middle-earth and attempted to guide Men through messages in the water. Lacking the skill of the Elves to perceive these messages, though, Men were drawn to the waters but did not know why.
Instead, Men learned much of the Moriquendi—Dark Elves—who had not set out on the paths to Valinor. Morgoth, being held in check by the new light, did not have the power to wander far abroad, and Men spread out over the land and many new things grew in Middle-earth. The peace was brief, however, as war with Morgoth grew nearer.
Unlike the Elves, Men are mortal and succumb easily to illness and accidents. Their fates after death is known by none save Manwë and Mandos (Námo), and it is speculated that perhaps the Valar do not even control their fates after death. This was not told in the Music. In the early years of Men in Middle-earth, Men and Elves fought side by side, and many were counted as heroes among the Elves.