Meriadoc Brandybuck:

Meriadoc Brandybuck was the son of the Master of Buckland. During the years of the War of the Ring, Merry (as he was usually called) was one of the Company of the Ring. When the Company reached Parth Galen, Merry and Pippin were both captured by Orcs. The two of them were forced to run across Rohan, though when the Orcs were surrounded by Éomer and the Riders, he managed to escape into Fangorn forest with Pippin. There they met Treebeard and joined the march of the Ents on Isengard. There after the destruction of Isengard they met the remaining members of the Company, along with Théoden and part of the host of the Rohirrim.

After the Winged Nazgûl was seen, Merry rode with the Rohirrim. When he reached the Hornburg, Merry swore service as Théoden's sword-thane. When they reached Dunharrow, he was told to stay behind with Éowyn. Merry disobeyed and was carried to the Battle of the Pelennor Fields by the knight Dernhelm, whom he later found to be Éowyn. Together they killed the Witch-king. Merry was healed of that encounter by Aragorn and was not present at the parley and the battle in front of the Black Gate. Merry was later named a Rider of Rohan and given the name Holdwine.

When the hobbits reached the Shire, Merry was one of the two captains that directed the two battles during the scouring of the Shire. After all this, he became the Master of Buckland.

In the year 64 of the Fourth Age, Merry and Pippin rode to Gondor where they remained until they died. Merry was laid in a tomb within the houses of the dead near the dead Kings. After the death of Aragorn, his tomb was placed next to that of Aragorn.

Melian:

A Maia, Melian became the wife of Elwë, and bore him a daughter, Lúthien. After Thingol's death, Melian returned to the West.

Mithrandir:

The Elvish name for Gandalf the Grey and later, Gandalf the White. Mithrandir is Sindarin and means 'Grey Pilgrim'. This name was also used in Gondor.

Melkor:

One of the Valar who chose to enter into Arda after it's creation by Ilúvatar. He was equal to Manwë in power. However, even during the Music, Melkor had wanted to take control. Almost from the first he made war on the others, corrupting numerous Maiar, including Sauron and the Valaraukar, or Balrogs.

The Ages of the Lamps, Trees, Stars and the First Age of the Sun were all dominated by the fight against Melkor in one form or another. However, there was one short break of six ages during the Ages of the Trees, when he had been imprisoned by the other Valar. Open war, this time against the Eldar and later the Edain broke out once again when Melkor stole the Silmarils from Fëanor. He was then renamed Morgoth. The account of these wars is told in the Silmarillion.

Morgoth:

The later name for the Vala Melkor. After Melkor stole the Silmarils, Fëanor renamed him "Morgoth" the Black Enemy of the World. It is by this name that he was ever after known. At the end of the First Age, Morgoth was removed from the circles of the World by the rest of the Valar. Among the many horrors attributed to Morgoth are, the breeding the race of Orcs and the creation of the race of Dragons, along with the death of the Two Trees and the theft of the Silmarils.

Mablung:

One of the two guards that Faramir left with Frodo and Sam in Ithilien. The other was Damrod.

Maglor:

One of the seven sons of Fëanor and his wife Nerdanel, Maglor was the second eldest. He was one of the best musicians in Middle-Earth. Along with his brothers, he swore the Oath of Fëanor, however when the Valar had recovered the two remaining Silmarils, he attempted to relinquish his oath. By this time, Maglor and his brother Maedhros were the only two sons of Fëanor still alive. Maedhros convinced him not to give up his claim to the jewels, though. When the Silmaril burned him, Maglor threw it in the sea. It is said that he wandered the coasts after that and no date is given for his death.

Maedhros:

Maedhros was the eldest of Fëanor's seven sons by his wife Nerdanel. Along with his brothers, he swore the Oath of Fëanor and left the Undying Lands in their attempt to recover the Silmarils.

He was captured by Morgoth through treachery and imprisoned on the peak of Thangorodrim. Maedhros was rescued by Fingon with the aid of the Eagle Thorondor, but he lost his right hand by which he had been chained to the mountain. However, he learned to use a sword with his left hand and became even more skilled with it.

During the War of Wrath, Maedhros, along with Maglor managed to regain the two remaining Silmarils, but they was burned by the one he took. As a result, "in anguish and despair he cast himself into a gaping chasm filled with fire"(S.305) along with the Silmaril.

Manwë:

The mightiest of the Valar, Manwë delights in winds and air. He often uses eagles as his messengers. His wife is Varda.

Míriel:

The first wife of Finwë. She died soon after giving birth to her only son, Fëanor. Miriel was greatly skilled in embroidery.

The Lord of the Rings
The Silmarillion
The Hobbit
The Complete Guide to Middle Earth by Robert Foster