You say it. I am the Elder King: Melkor, first and mightiest of all the Valar, who was before the world and made it. The shadow of my purpose lies upon Arda, and all that is in it bends slowly and surely to my will. But upon all whom you love my thought shall weigh as a cloud of Doom, and it shall bring them down into darkness and despair. Wherever they go, evil shall arise. Whenever they speak, their words shall bring ill counsel. Whatsoever they do shall turn against them. They shall die without hope, cursing both life and death.
~ Morgoth boasting of himself to Hurin while giving him a curse and lying about creating Arda, The Words of Hurin and Morgoth.
Morgoth, originally named Melkor, is the main antagonist of the Arda universe of J.R.R. Tolkien, which is mainly focused on Middle-earth, and ultimately, the main antagonist of the Middle-Earth legendarium.
He is an evil Vala and the first Dark Lord of Middle-Earth. He is also the master and predecessor of Sauron. Morgoth is also the de-facto ultimate evil of the whole universe, known as Eä.
Middle-earth: Shadow of Mordor
Morgoth himself never appears in this game; however, there is a graven idol representing him, which can be found in the western part of Udûn.
And he descended upon Arda in power and majesty greater than any other of the Valar, as a mountain that invades in the sea and has its head above the clouds and is clad in ice and crowned with smoke and fire; and the light of the eyes of Melkor was like a flame that withers with heat and pierces with a deadly cold.
~ The Silmarillion on Morgoth's coming to Arda.
When he first came to Arda, Melkor took the form of a gigantic, ice-white humanoid being, filled with flames. This form was terrifying; it was the size of a giant mountain, with his head just touching the uppermost clouds. This projected his arrogance, greed for power, and hatred of his Valarian siblings on the early Arda, and it severely damaged the world with its mere presence alone.
The more time Morgoth spent in the world, the more his dark leaked into it, and corrupted what his Father Eru had originally designed. As time went on, he became manifested as the Dark Lord when his shapeshifting abilities were stripped from him from all of the evil he was committing. As the Dark Lord, he was superhumanly tall, approximately 500 feet, "like a tower", and covered in dark storm clouds and a dark powerful aura which humbled all who saw him. He wore an Iron Crown at all times, as his means of others identifying him with kingship of the world, and he placed the Silmarils in his crown when he had stolen them.
…hatred devoured him, and in the domination of his servants and the inspiring of them with lust of evil he spent his spirit.
~ The Silmarillion (on Morgoth).
Morgoth was a very standoffish, intimidating, and unapproachable opponent, because of his being in the presence of Ilúvatar had given him almost godlike powers. However, he was a skilled, influential, and manipulative politician and could charm his enemies, as he tried to do with Hurin when he captured him.
When seen as Melkor, he was perceived as resplendent, majestic, and noble, even by his enemies, but when he became Morgoth, he became a giant looming threat which was feared by even the noblest warriors on Earth. Literally only five people on Earth ever challenged him: Fingolfin, Beren and Luthien, Hurin, and also Earendil. This clearly shows his formidable and authoritative might, with Fingolfin being the only one to ever enter into a duel with him. Although Morgoth won the duel, Fingolfin gave him seven wounds, which clearly shows Morgoth's power, (albeit diminished due to his evils) because if a skilled Elf swordsman could only give Morgoth seven wounds then he was clearly impressive, resilient, powerful, and durable.
Unlike the other Valar, Morgoth knew fear and pain. This was most likely a punishment given to him because of his heinous and iniquitous crimes. He could feel the pain of the Silmarils, and also the wounds given him by Thorondor the eagle, and Fingolfin scarred him forever and caused him a burning pain. Luthien commented that Morgoth's life was a "burden", and she rid him of this "burden" for awhile by putting him into sleep.
Morgoth was also very domineering and arrogant, as he loved challenging people and reducing their wills to dust. He prided himself on his immense powers, giant size, and intelligence, and knew that he would most likely come off better in any duel. However, these tables got turned in his epic downfall.
Morgoth may rank as one of (if not the) most evil, terrifying, and powerful antagonist in fiction, because he was almost successful in his goals, and it literally took everyone's will to defeat him.
Abilities and Weapons
Morgoth was the greatest of the Valar. He, like Sauron, was functionally immortal; failing that, seemingly very long lived having existed with and without a physical form for the better part of several thousand years. (Morgoth was created before the physical realm of Arda and Middle Earth was established thus his age is un-quantifiable. Assuming a consecutive lifespan, he's at least 50,000 years old).
Being the greatest of all the beings Eru Ilúvatar had created, Morgoth was gifted with the greatest power and the greatest intelligence, second only to Eru. However, he used his gifts for evil purposes, such as torturing Elves into Orcs and creating creatures which were not in accordance with Ilúvatar or the Valar (including Trolls and quite possibly Dragons).
Like his servant Sauron, he was capable of altering the physical substance of the world around him by mere effort of will. He could cause massive firestorms, create huge craters, and give curses to his foes. Also, by using his mace, Grond, Morgoth can cause lightning strikes and create pits where lava and smoke come out of the ground. In his mountain-sized humanoid form, he was able to do excessive damage to Arda while the other Valar were doing work there.
Do as I bid; and if thy hunger still when all is done, then I will give thee whatsoever thy lust may demand.
~ Morgoth telling Ungoliant to follow him and giving her a false promise.
Yet I may come at you, and all your accursed house; and you shall be broken on my will, though you all were made of steel.
~ Morgoth to Hurin.
Behold! The shadow of my thought shall lie upon them wherever they go, and my hate shall pursue them to the ends of the world.
Fool, little among Men, and they are the least of all that speak! Have you seen the Valar, or measured the power of Manwë and Varda? Do you know the reach of their thought? Or do you think, perhaps, that their thought is upon you, and that they may shield you from afar?
~ Morgoth to Hurin about the Valar.
What wouldst thou have more? Dost thou desire all the world for thy belly? I did not vow to give thee that. I am its Lord.
~ Morgoth to Ungoliant.
Nay! Thou hast thy due. For with my power that I put into thee thy work was accomplished. I need thee no more. These things thou shall not have, nor see. I name them unto myself forever.
~ Morgoth refuses to give Ungoliant the Silmarils.
Pertaining to Morgoth
Then Ilúvatar spoke, and he said: ‘Mighty are the Ainur, and mightiest among them is Melkor; but that he may know, and all the Ainur, that I am Ilúvatar, those things that ye have sung, I will show them forth, that ye may see what ye have done. And thou, Melkor, shalt see that no theme may be played that hath not its uttermost source in me, nor can any alter the music in my despite. For he that attempteth this shall prove but mine instrument in the devising of things more wonderful, which he himself hath not imagined.‘
~ J.R.R. Tolkien about Ilúvatar despising Morgoth about his music, The Silmarillion, Ainulindalë.
Now news came to Hithlum that Dorthonion was lost and the sons of Finarfin overthrown, and that the sons of Fëanor were driven from their lands. Then Fingolfin beheld… the utter ruin of the Noldor, and the defeat beyond redress of all their houses; and filled with wrath and despair he mounted upon Rochallor his great horse and rode forth alone, and none might restrain him. He passed over Dor-nu-Fauglith like a wind amid the dust, and all that beheld his onset fled in amaze, thinking that Oromë himself was come: for a great madness of rage was upon him, so that his eyes shone like the eyes of the Valar. Thus he came alone to Angband’s gates, and he sounded his horn, and smote once more upon the brazen doors, and challenged Morgoth to come forth to single combat. And Morgoth came.
~ J.R.R. Tolkien about Morgoth face-to-face with Fingolfin, The Silmarillion, Quenta Silmarillion: Of the Ruin of Beleriand and the Fall of Fingolfin.
Therefore Morgoth came, climbing slowly from his subterranean throne, and the rumour of his feet was like thunder underground. And he issued forth clad in black armour; and he stood before the King like a tower, iron-crowned, and his vast shield, sable unblazoned, cast a shadow over him like a stormcloud. But Fingolfin gleamed beneath it as a star; for his mail was overlaid with silver, and his blue shield was set with crystals; and he drew his sword Ringil, that glittered like ice.
~ J.R.R. Tolkien describing Morgoth's might as the latter and Fingolfin are about to challenge each other, The Silmarillion, Quenta Silmarillion: Of the Ruin of Beleriand and the Fall of Fingolfin.
Morgoth held hurled aloft Grond, Hammer of the Underworld, and swung it down like a bolt of thunder. But Fingolfin sprang aside, and Grond rent a mighty pit in the earth, whence smoke and fire darted. Many times Morgoth essayed to smite him, and each time Fingolfin leaped away, as a lightning shoots from under dark cloud; and he wounded Morgoth with seven wounds, and seven times Morgoth gave a cry of anguish, whereat the hosts of Angband fell upon their faces in dismay, and the cries echoed in the Northlands.
~ J.R.R. Tolkien recounting the duel between Morgoth and Fingolfin, The Silmarillion, Quenta Silmarillion: Of the Ruin of Beleriand and the Fall of Fingolfin.
Morgoth set his foot upon his neck, and the weight of it was like a fallen hill.
~ J.R.R. Tolkien about Morgoth defeating Fingolfin, The Silmarillion, Quenta Silmarillion: Of the Ruin of Beleriand and the Fall of Fingolfin.
Allusions in Other Works
Morgoth appears as a character in Legendary Frog's parody series of flash videos, One Ring to Rule them All. Ironically, he only appears in the third video.
In the 3rd video, Melkor acts as Sauron's old master (or college roommate), and gives him a visit. However, he steals his spices and seasonings for Legolas.
How Morgoth created the Orcs is up for much debate, because Tolkien himself says "Who has explored the mind of Morgoth?" This being said, the creation of Orcs is entirely open to speculation.
There is a disturbing theory that, as Orcs are bow-legged, Morgoth smashed their legs in repeatedly, thus breaking them, and over time their descendants "healed" to being a bow-legged creature. Also, their elongated arms could be the result of Morgoth gruesomely stretching them on racks or from his hanging them from chains on high vaulted subterranean halls. And finally, their charred black skin could simply be the result of his burning them alive through intense flame.
While not appearing in the film series (most likely because he no longer existed in the world at the time of the said series because of his banishment to the Void in the War of Wrath in The Silmarillion), Morgoth's most powerful servants such as Sauron still thrive, and Morgoth was mentioned in The Lord of the Rings: The Two Towers as when Gandalf speaks of his battle with the Balrog, he refers to it as "The Balrog of Morgoth". He was also mentioned in The Hobbit: The Battle of the Five Armies when Galadriel calls Sauron "Servant of Morgoth".
Ironically, Morgoth was not even mentioned in the novel of The Hobbit, because by that time, Tolkien had not yet conceived his mighty mythology, and he had only begun to create the barest aspects.
Morgoth appears in his earliest incarnation in the novels Unfinished Tales which compare the earliest scripture of The Lord of the Rings with the final version. In this version, Morgoth is named Melko instead of Melkor, and is either another name for him or an epithet of Melkor itself.
Sauron is said by Tolkien to have been certainly more successful than Morgoth, given that Sauron was far more cunning, and possessed shape shifting and deception to fool others. Morgoth is compared to Sauron by Tolkien because the whole Earth was "Morgoth's Ring". However, Morgoth is much more evil, powerful, and majestic, than Sauron, and is not to be overlooked or taken lightly.
It might be a bad thing if Dagor Dagorath happens because Morgoth is supposed to die in the prophecy, and if he dies, the balance between good and evil will collapse because he is the ultimate evil in Middle-earth. However, it is possible that Morgoth may be revived somehow and imprisoned once again when the prophecy is fulfilled, this time for good.