This is off the subject of art (although I'll get back to it sooner or later) but I'm into this so I decided to write about it instead.
I love Beowulf. You've got a big monster fight, then an abduction, then a lake full of firesnakes, then an even badder monster fight, and then a dragon. Awesome.
I also like Tolkien, of course (I say of course, because anyone who read that last paragraph without glazing over or having bad flashbacks from high school English probably also likes Beowulf and Tolkien). In his essay "Beowulf: The Monsters and the Critics" Tolkien says, among a lot of other excellent things, that Beowulf is a type of "Bear's Son" tale. This sounded equally awesome, since that must mean that there's some kind of ur-Beowulf tale out there, of which the Beowulf poem is a reflection. So I set out to find out what that was (I'm a primary-sources kind of guy).
Unfortunately, that seems to be all anyone says about it, that that's exactly what Beowulf is. They don't define this thing that is supposed to sum up Beowulf, which makes me wonder what the point is to summing it up that way. Instead of a helpful analysis tool it ends up making everything even more obscure than it already was (origin-wise, that is - it's hard to be obscure about monster fights).
Finally, I found a book called Beowulf and the Bear's Son (by J. Michael Stitt). This did, in accordance to the title, actually describe the Bear's Son tale. Reading it, I learned two important things:
1. The reason no one tells me what the Bear's Son tale is about is that no one calls it that any more. If it's referenced at all, it's called the "Three Stolen Princesses" tale, so if you're looking it up, check that instead.
2. Even if you look up the "Three Stolen Princesses," the theory that Beowulf is a version of it is just wrong.
Unlike the story it is supposed to be based on, Beowulf doesn't have any stolen princesses. He also doesn't have three companions that specifically try to kill him, nor does he get back out of Grendel's mere via griffin, magician, or magic playing card. Granted, all of those are cool, as is the stolen princesses story, but it won't really help you understand Beowulf.