Who the heck is Tom Bombadil in The Lord of the Rings?

On Nerd of the Rings, Matt explores the question that many readers of The Lord of the Rings come away with. Who is Tom Bombadil? He is obviously some kind of spirit of nature, and appears to be as old as Middle-earth itself. But where did he come from? What he is? Is he an expression of Eru himself? Is he a Vala? A Maia? Matt explores 5 common theories about Bombadil.

I love the theory that he's actually an embodiment of the music of Ainur, the music that created the universe. I also love a theory not covered in the video, but is brought up in the YT comments: "I think that Tom is actually Tolkien. He saw the first raindrops and acorns because he wrote them, and he doesn't interfere greatly with the storyline for the sake of the readers."

Image: Screengrab