A town is menaced. An outsider comes to town. The outsider may be wild, but he's the only hope the town has for dealing with the menace. And the outsider ends up beating the menace and saving the town.
Now: have I just told you the plot to Beowulf or the plot to a standard Western story? And you should probably say "Both!"
This might sound familiar to you since I said almost the exact same thing a little over a year ago. But I think it bears repeating: You could easily make Beowulf a western where a group of gunslingers comes to an isolated long hall/town and needs to fight off a monstrous enemy--who might have an even more monstrous mother.
In fact, these two stories are so obviously related that combining them might not give you too much pleasure. I mean, you can give Beowulf a six-shooter and make a fun comic book, but you're probably not going to get out any of the dark inspiration that keeps you going as an artist.
But still--why aren't you writing... Icelandic Saga Westerns?