Sure.

My daughter is 17 months old, and I cringe every time I hear about a parent losing a child -- although I cringed before as well. I never did like to watch the local news. On the other hand, there is only so much I can do to protect her, and obsessing about it won't protect her at all.

   Morgoth personally was cast into the void beyond the walls of the world, not to return until the end of time. But he had infused so much of his personal power into the fabric of Middle-Earth that the whole place is more or less hot with evil radiation (he was particularly fond of gold, and hence it tends to be a special focus of evil).   I find it very helpful to think of Morgoth's corruption of the earth in terms of radioactivity; there's a little bit of it everywhere (background Morgoth), and it can be concentrated and/or used as a power source.
   Sauron no doubt employs the power of Morgoth routinely, and may have special access to it through Mt Doom (most of Morgoth's power, after all, went deep into the earth). He may have some way to commune with the spirit of Morgoth, although Morgoth is outside the world and technically dead.
   The key thing to understand, though, is that Morgoth was a vastly greater power than Sauron. As Sauron's One Ring radiates temptation and corruption, because it hold the greater part of Sauron's power, so too does the fabric of the earth, the vessel of Morgoth's power, do the same thing; all the world is Morgoth's Ring. This means that we are constantly under assault from evil impulses, and our perceptions are under the Shadow (so, for instance, we may even find fault with the Valar's governance of the world!). In effect, the essence of Morgoth becomes an external cause of what theologians call the Depravity of Man.
   Because of the corruption of all matter, Elves' bodies will not last forever, as intended. This is a problem for their souls, which WILL last forever. Hence, elves in Middle-Earth will eventually 'fade' into something very like a wraith. Apparently the Elven-Rings can hold this effect at bay over a limited area. This is what it means when Elrond says that they have great power to preserve all things unstained - they can exclude the Morgoth-taint, so that places like Rivendell and Lorien give us a glimpse of what Arda Unstained should have been like. The failure of the Elven-Rings after the War of the Ring is why all the Elves who could HAD to sail west; to avoid fading.
   And that should hold you for now.

-- Reverend's explanation of Morgoth's taint. R.I.P., Reverend.