Beowulf was a fictional hero past down by word of mouth for generations. The story of Beowulf was able to stir the hearts of its reader for generations. How is it, however, that this story was able to keep its audience enraptured for so long? The answere is simple; the story changed.
One of the ways that the story changed is through the villain Grendel. In the original poem Grendal was a blood thirsty tyrent whos only interest was to reak havock on Hrothgard's men. In the movie Beowulf and Grendal however, Grendel had a reason for doing the things that he did. A cause; and that was to avenge his father and wrong the people who had wronged him. Grendal had a cause.
The second thing that changed through the story was the hero himself. In the movie Beowulf was fighting for a cause and choosing the side for which he would fight. It showed that he was Noble vs Ignoble and that killing Grendel was more than just a job to him, which is what was different than in the story.
These transformations have occured in order for the story to fit its audience. Over time culture and morality has changed just the poem has. Beowulf is telling a story of heroism that pertains to us today. Our modern day soldiers could be compared to Beowulf as terroists could be compared to Grendal.
Beowulf will continue to be changed as time goes on and it will continue to stir the hearts of it's audience.