The concept of evil is in The Silmarillion represented by Melkor, whose similarity to Satan is even greater than that between Eru and God. Melkor was the greatest of the Ainur with a share in the powers of all the others of his kind. Originally, he was a brother of Manvë in Ilúvatar’s mind (Tolkien, 1992, p. 16). Likewise, Satan was the greatest and cleverest Angel with power equal to Michael until he was cast out of Heaven because of his rebellion against God. And that is another similarity of these two. As it is generally believed, Satan was so proud of his big power that he soon became jealous of God. He did not want to serve Him anymore; instead, he wanted to usurp the whole World for himself. He did not want to worship God, but he desired to be worshipped himself. So he revolted against God. The account for this is given in the Book of Isaiah: “How art thou fallen from heaven, O Lucifer, son of the morning! how art thou cut down to the ground, which didst weaken the nations! For thou hast said in thine heart, I will ascend into heaven, I will exalt my throne above the stars of God,” (Isaiah 14, 12-13). And he was joined by many lesser angels, whom he was able to persuade. For this reason Michael the archangel had to fight him and expelled him and all his followers from Heaven.

Similarly, Melkor revolted against Ilúvatar. When he saw that the things pre-imagined in the Great Music were wonderful, they attracted him so much, that he desired to own them all, to govern them and be the king of the whole World instead of Ilúvatar. Like Satan, he did not want to participate in Ilúvatar’s plan only as his mediator, but he was anxious to use his great power to create things of his own that were not in correspondence with Ilúvatar’s will. Tolkien perfectly depicted his revolt in the scene when Ilúvatar and the Ainur sang the music of creation. Melkor did not follow Ilúvatar’s melody; instead he sang differently to his own tune. And many of those who heard him were distracted and charmed by his ideas and joined him (Tolkien, 1992, p. 5). And the following excerpt exactly expresses the general perception of Satan’s fall, even though it is applied to Melkor: “From splendour he fell through arrogance to contempt for all things save himself, a spirit wasteful and pitiless. Understanding he turned to subtlety in perverting to his own will all that he would use, until he became a liar without shame. He began with the desire of Light, but when he could not possess it for himself alone, he descended through fire and wrath into a great burning, down into Darkness,” (ibid., p. 23). So the concept of fallen Ainu is identical with fallen angel, for they both refused to subordinate to a higher authority of the Creator, but wished to replace it by themselves.

Also their names are very similar in the meaning. According to Tolkien, Melkor means “he who arises in Might” (ibid., p.410) what symbolizes his position among the Ainur at the very beginning, before the creation started. On the other hand, one of Satan’s else names, Lucifer, refers to his original purpose, too. Because in Latin Lucifer means “light-bringing” or, as it was already alluded in the quote from Isaiah above, “the morning star”  (http://catholic.archives.nd.edu/cgi-bin/lookup.pl?stem=luc&ending=). This name signifies Satan’s primary function, for as the greatest angel he had to be the one most engaged in bringing people to God or vice versa to bring the God’s light and Love to people. But after his fall he has been named mostly Satan. Its meaning can be derived from various stems, but it is usually translated as “the opposer” or “the adversary” or simply “the enemy”. And Melkor was in the Eä renamed to Morgoth which has again similar meaning and that is “the Dark Enemy of the World,” (Tolkien, 1992, p. 23). Even Devil, which is probably the most common name of Satan, is in concordance with the above-mentioned idea of a liar. Because it was derived from Greek name Diabolos which means “slanderer” (see http://biblesuite.com/greek/1228.htm) what is actually a synonym of liar. And no less important is the fact that Melkor refers to himself as “the Eldest King” (Tolkien, 2006, p. 77, translated by the author of this work) too, for he was created as the first of all the Ainur, like Satan, who is said to be the first of all angels.

Consequently to the fall, as soon as he was driven out of Heaven, Satan inhabited the Earth and claimed it to be his property, his kingdom. And in the Bible he is therefore called “the prince of this world” (John 12, 31). Same it is with Melkor, even though he was not forced to leave the “Outer Circles” by anyone and it was his own decision to move to Eä. But in his pride and selfishness he called himself “the Lord of the World” too, as it is several times noted in The Silmarillion. And he cannot be destroyed while the World lasts, same as Satan cannot be destroyed until the Apocalypse.

But despite all his attempts and desires, Melkor cannot create anything of his own, no matter how big his power was. This again relates him to Satan who “has no ability to create”1 as well. They can only make, that is only transform and disfigure things that were created by the Creator. Tolkien explained this disability to create in one letter to his reader, in which he distinguished between creating and making. He notes that creating is “the act of Will of Eru the One that gives Reality to conceptions” (Carpenter, 2006, p. 190) while making is understood as permissive manufacturing. Only God can create in the true sense of the word, because he is the only one who can give life to non-living things. The Evil simply cannot give life for he has not been given the power. In this way both Melkor’s and Satan’s abilities were limited. 

And the last point that should be considered is the consequences of Evil’s doings. In The Silmarillion, Melkor, like Satan, often misuses many good qualities in a bad manner; for example, he pretends to be merciful and kind only in order to fool people and to force them to do what he wants. But everything he does always results in misery and torments. However, even all the action of Evil does, after all, contribute to the Creator’s plan. The Christian doctrines say that God works in all actions of His critters and that He, in His almighty Providence, can derive Good from the aftermaths of Evil. And the Evil cannot in any way thwart God’s plans (Catechism, Section Two, Chapter One). Everything what Satan does has rather opposite effect and it only multiplies God’s glory. Because in order to heal, what Satan damaged, God again and again shows His prevailing power. And even suffering will be soon or later rewarded by blessing. 

Tolkien understood this very well and he implemented this theory into his writing. In the scene when Melkor revolted against Ilúvatar by singing to a different tune, Ilúvatar successfully managed to integrate it into his primary melody, so it sounded harmonious. And then 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,” (Tolkien, 1992, p. 4-5). And later the allusion to Christian doctrines is even more explicit in Ilúvatar’s words: “These [all critters] too in their time shall find that all that they do redounds at the end only to the glory of my work,” (ibid., p. 36). By this statements Tolkien conveyed the principal belief of Christianity that Evil can do only as much as it has been allowed by God and even then it contributes to His intentions.

Resources:

Catechism of the Catholic Church

CARPENTER, H. (ed.), The Letters of J.R.R. Tolkien, 2006, London: HarperCollins, 1981. 502 pp. ISBN 978-0-261-10265-1

TOLKIEN, J.R.R., The Silmarillion, 1992, London: HarperCollins, 1992. 480 pp.            ISBN 978-0-261-10273-6

TOLKIEN, J.R.R., The Unfinished Tales,  2000, London: HarperCollins, 2000. 611 pp. ISBN 978-0-261-10215-6

http://biblesuite.com/greek/1228.htm

http://catholic.archives.nd.edu/cgi-bin/lookup.pl?stem=luc&ending=

http://www.abarim-publications.com/Meaning/satan.html#.UWBUiZPvjeE