Of the Coming of the Elves and the Captivity of Melkor
Of the Coming of the Elves and the Captivity of Melkor tells of several instrumental events in the Legendarium. It begins with the Valar at war with Melkor, who has sewn evil in Middle-Earth and built a great fortress Utumno. It speaks of the Valar primarily, as they ready Arda for the coming of the Firstborn, the Elves. Tulkas makes war on Melkor while Varda prepares the world by placing the stars in the sky to guide the Elves in the darkness of Middle Earth. All is prepared for the coming of the Elves.
The next major event is Melkor's captivity. Melkor has built up great strength in Utumno, and created Orcs in mockery of the Elves. This was said to be the most evil deed of Melkor. The War on Melkor is presumably won. Utumno is sacked, though Tolkien notes there are deeper and mighty vaults in the fortress that were unchecked, and so evil continued. Additionally, one of the Maia who fell with Melkor, his lieutenant Sauron, was not found and thus escaped. But Melkor was found cowering in the depths of Utumno, and Aulë wrought chains to keep him in captivity.
The final major event of this chapter is the coming of the Elves, Firstborn of Ilúvatar. This actually takes place while the War for Sake of the Elves is happening, and so is simultaneous rather than final. It is said, however, that the Elves heard a great shaking and were worried but did not take part in the battle. The first elves are described to have greater stature than their descendants, but are just as fair. They marvel at nature, the stars, etc. This chapter not only describes the original thoughts of the elves and their surroundings, but also the Great Journey and the sundering of the Elves. The Valar send servants to call them to Aman. The Elves embark on the journey across Middle Earth, save some who refuse, and are further called dark Elves, or the Avari. The Elves' journey, and some fall off along the way, who are called the Teleri. They are sundered in many groups, but they eventually reach Beleriand by the sea. Here more Teleri stay, for their love of the ocean. Finally those who journey across the sea to Aman are called the Eldar. Some of the Teleri, too, reach Aman, and are guided by Swan boats. From here on the Elves are sundered into groups, and these divisions would prove important later.
 Sundering of the Elves