Where does God fit in?
To the extent that there is metaphor of Christ that is God.
John 1
The Word Became Flesh
1In the beginning was the Word, and the Word was with God, and the Word was God. 2He was with God in the beginning.
3Through him all things were made; without him nothing was made that has been made. 4In him was life, and that life was the light of men. 5The light shines in the darkness, but the darkness has not understood it.
6There came a man who was sent from God; his name was John. 7He came as a witness to testify concerning that light, so that through him all men might believe. 8He himself was not the light; he came only as a witness to the light. 9The true light that gives light to every man was coming into the world.
10He was in the world, and though the world was made through him, the world did not recognize him. 11He came to that which was his own, but his own did not receive him. 12Yet to all who received him, to those who believed in his name, he gave the right to become children of God— 13children born not of natural descent, nor of human decision or a husband's will, but born of God.
14The Word became flesh and made his dwelling among us. We have seen his glory, the glory of the One and Only, who came from the Father, full of grace and truth.
15John testifies concerning him. He cries out, saying, "This was he of whom I said, 'He who comes after me has surpassed me because he was before me.' " 16From the fullness of his grace we have all received one blessing after another. 17For the law was given through Moses; grace and truth came through Jesus Christ. 18No one has ever seen God, but God the One and Only, who is at the Father's side, has made him known.
Some very interesting insights into his views of God and Creation.
Tolkien had his own mythology but bits of the Christian one peep through nearly everywhere. This, for instance:
(Gandalf speaking) "Bilbo was meant to find the Ring, and not by Sauron."
These are very deep waters. I would suggest ignoring the movies - they are lush realizations of the visual aspects of LOTR but so superficial as to be useless when discussing what Tolkien actually meant. There are as many different interpretations of LOTR's congruence to Christianity as there are commentators, but there are a few themes that are basic to the argument.
Both Frodo and Gandalf are very unsatisfactory Christ-figures, the one because his sacrifice was, in the event, unsuccessful, and the other his was not a willing sacrifice but a casualty of war. One does not need to be a Christ figure to sacrifice what is dearest so that others can retain it. Frodo is much closer to a metaphor for those WWI veterans with whom Tolkien served, IMHO, who gave up sight and health and life so that England could remain England. They were not Christ but mere men, and so, in the end, was Frodo.
One central theme that is common both to LOTR and to Christianity is redemption, and it is explored in several forms - Boromir, Theoden, Eowyn, Frodo himself, and especially that most interesting character in LOTR, Smeagol/Gollum. I think it is exquisitely clever that his fall constituted Frodo's redemption and vice versa.
Great literature holds great ideas, and LOTR qualifies in every regard. Do not be disappointed if there are multiple answers to these sorts of questions.