Having recently seen 300, an infinitely superior film to this, it came to mind that this was probably used as Gerard Butler's audition. In Beowulf & Grendel he shows that he has a certain charisma in the hack-and-slash type of film, and can spout inspirational dialogue at high volume.
This is not to say that this is a good film, just to say that it can be used to fill certain uses by those who have chosen to be in it. I also do not mean to imply that Butler may have had any type of ulterior motive, just expressing a thought that came to mind as I watched. As for the film itself, well it is not a complete trainwreck, but it is not exactly good either. There are elements that worked well, and I like the idea that gave it birth.
I am not all that familiar with the original Beowulf poem, aside from reading portions of it many years ago in high school, and liking it. It is a grand tale of vengeance, a violent story of revenge, and the perfect fodder for an engrossing film. Sadly, this film is not that pure telling of the story that I may have hoped for, but it is an intriguing alternate take, a "what if" if you will. The end of the film — and I am sorry to spoil this, but I feel it is necessary — reveals that the author of the original epic may have been a contemporary of the real Beowulf. Essentially, this was conceived as the real story that the poem may have been based on, a tale with real world origins that was exaggerated over the years into what it would become.
The story tells of King Hrothgar (Stellan Skarsgård), who many years ago led a hunting party against a troll that had been harassing the village. Once the deed was done, Hrothgar spies the creature's child and chooses to spare the young one's life. This sets the child along a path of vengeance. We then pick up the story some years into the future. Hrothgar is depressed, and not much of a leader at this point. The child troll, now an adult, emerges from the night to slaughter the Dane soldiers in retaliation for the murder of his father. His goal seems to be Hrothgar himself.