634-635). What he means by this is that the people have wished for him to put an end to Grendel, and he's saying that it is his duty to do so or he himself will die. Beowulf has a unique quality of strength that allowed him to be much stronger than the average man of his time. This, along with his bold attitude made him a more than perfect candidate to battle the evil and deadly beast. "I shall perform a deed of manly courage, or in this meadhall I will await the end of my days!" (l.634-637). Beowulf says as he announces to take on the dangerous task. He specifically states that it is a deed, as if it's something mandatory because he will not live if he doesn't do it. Hrothgar says to Beowulf at the end of the passage, "I have never entrusted to any man, ever since I could not hold and hoist a shield, the great hall of Danes- except to you now." (655-657). Hrothgar is entrusting Beowulf to do something he has never asked anyone to do. This shows that by Beowulf taking on Grendel, he is performing a critical duty asked of him by Hrothgar.
This is an extremely crucial and important part of the story as a whole. It allows the audience to really gather the concept of what the story will entail and what Beowulf is going to have to accomplish on many different levels. He has to destroy Grendel, as a mission given to him to protect the people. It isn't against his will, however a choice he does have, but the alternative is unattractive to him. It lays out the foundation of Beowulf's purpose as a member of society, as well as his service to himself. He believes it is his duty in society to protect people, while at the same time fulfill the purpose of his own life. This passage gives purpose to the audience to continue on with the story to find out if Beowulf fulfills this imperative mission, and makes it to the end. But most importantly it tells the audience the purpose of Beowulf's intentions to take on Grendel.