Why did Beowulf go to Heorot?

Beowulf, a mighty warrior living in Geatland, learns that Grendel has been attacking Heorot, the great mead hall in Denmark built by Hrothgar. Beowulf therefore decides he must kill Grendel. He takes 14 of his best warriors and sails for Denmark.
Heorot, as a mead hall, is a symbol of civilization—of warmth, food, fellowship, and security—so Beowulf's decision to defend it places him on the side of all that is good, protecting human society from chaos and barbarism.
Hrothgar is glad to have Beowulf arrive. Hrothgar thinks that, in addition to friendship, Beowulf has come to repay him for helping Beowulf's father, Edgetho, avert a war with the Wulfings years ago. Hrothgar orders a great feast to celebrate the arrival of Beowulf and his men. That night, Grendel attacks, and Beowulf rips off his arm with this bare hands, for the soldiers' weapons have been bewitched by Grendel and are useless. This loss of an arm mortally wounds Grendel.