What is the main conflict in The Silmarillion by J.R.R. Tolkien?

Ea, the World that Is, is created, and the Valar prepare the way for the Children of Iluvatar. Along the way, the Valar and the Children of Iluvatar battle evil in the form of Melkor in order to survive and maintain good in Ea. The Silmarillion parallels the Christian story of creation in many ways but still manages to introduce its own mythology of the creation of the world and humanity.