I try to keep Splettnet.net away from any sort of heated third-rail controversy, but kind of think I have pretty much cracked the code on the Tom Bombadil enigma from Lord of the Rings. As per the LOTR Wiki, there has been a LOT of speculation on the matter:
The most common theory is that Bombadil is a Maia, supported by his claim that, “Tom remembers the first raindrop and the first acorn […] he knew the dark under the stars when it was fearless — before the Dark Lord came from Outside.” Morgoth, the Dark Lord, was the very last of Ainur to enter Arda (excepting Tulkas); all the other Valar and Maiar, as per Tom’s description, had existed there for some time before his arrival.
“Other possibilities (compatible with the above theory) are that he is an abstract concept; possibly the embodiment of Arda Itself, a veritable “Father Nature”, or some kind of ‘spirit’ which, unlike the Maiar, was of a non-divine nature. Not only does the Ring have no effect on him, but Tom himself seems unable to affect the Ring in return. This shows that Tom was outside the divine plan and struggle and had no position in it. During the Council of Elrond it is suggested that the Free-Peoples entrust the Ring to Tom, but this is rejected due to the probability that he would lose it, because according to Gandalf, such things had no hold on his mind. It is also stated that if Sauron were to regain the Ring, Tom Bombadil would be the last to fall. It is also stated by Galdor that ‘Power to defy our enemy is not in him, unless such power is in the earth itself. And yet we see that Sauron can torture and destroy the very hills.’ implying that Bombadil is in some way connected with the very earth itself.”
So, no one really knows and, when last I checked, J.R.R. Tolkien is not around to tell us!
P.S. I am referring to LOTR, the books, and LOTR, the movies, but not any of the LOTR video games, some of which are waaaay off-canon IMHO.