What were the poets singing about in the mead hall?

The scop, or bard, sing about Beowulf after the defeat of Grendel. They also mention the great warrior Sigemund, who slayed a dragon (foreshadowing) and the evil King Heremod. The bard's stories of Sigemund and Heremod reflect on the greatness of Beowulf by comparison and contrast, respectively.