Beowulf is loosely divided into three parts, each of which centers around Beowulf’s fight with a particular monster: first Grendel, then Grendel’s mother, then the dragon. One can argue that this structure relates to the theme of the epic in that each monster presents a specific moral challenge against which the Anglo-Saxon heroic code can be measured and tested. Beowulf’s fight with Grendel evokes the importance of reputation as a means of expanding one’s existence beyond death. Grendel’s great and terrifying nature ensures that Beowulf will long be celebrated for his heroic conquering of this foe. His subsequent encounter with Grendel’s mother evokes the importance of vengeance. Just as Beowulf exacts revenge upon Grendel for killing Hrothgar’s men, so too must Grendel’s mother seek to purge her grief by slaying her son’s murderer. Beowulf’s final encounter with the dragon evokes a heroic approach to wyrd, or fate. Though he recognizes that his time has come and that he will thus not survive his clash with the dragon, he bravely embraces his duty to protect his people, sacrificing his life to save them.
Alternatively, one might make a division of the text into two parts, examining youth and old age as the two distinctive phases of Beowulf’s life. Along these lines, the gap of fifty years between the first two conflicts and the last marks the dividing line. One of the main thematic points highlighted by such a division is the difference in responsibilities of the warrior and of the king. As a young warrior, Beowulf is free to travel afar to protect others, but as an old king, he must commit himself to guard his own people. Additionally, whereas Beowulf focuses on the heroic life early on, seeking to make a name for himself, he must focus on fate and the maintenance of his reputation late in life.