This tale deals with three main themes: The Hiding and protection of Valinor, The Gates of Night and Morn and the passages of the Sun and Moon, and finally, The Counting of Days, Months and Years.
The tale of this chapter concerns how Melko manipulated the Noldoli in order to get hold of the the precious gems that they had made and to create distrust towards the other gods. The chapter also features the theft of the Silmarils and the ruin of the Trees of Light.
This passage is basically the first part of the creation myth that Tolkien designed for the world he wrote about. It tells about how Ilúvatar sang the Ainur into being and how the world and elements became real. The story mainly deals with Ilúvatar's vision and design of the world - through music.