Beowulf's behavior before and during his battle with Grendel is courageous, proud, and honorable. Beowulf, when he hears of Hrothgar's plight, doesn't hesitate to assemble a band of men to travel across the sea and take on Grendel, who threatens all of civilized human life with his attacks on the mead hall.
When Beowulf arrives at court, he shows his understanding of the proper forms of address, as well as a great deal of pride, when he tells Hrothgar and his men of his remarkable abilities in battle:
So every elder and experienced councilman
among my people supported my resolve
to come here to you, King Hrothgar,
because all knew of my awesome strength.
They had seen me boltered in the blood of enemies
when I battled and bound five beasts,
raided a troll-next and in the night-sea
Beowulf is stating that he is an exceptional fighter. To add to the pressure on Beowulf, his story is discounted as bragging by Unferth, one of Hrothgar's men. Beowulf, whose integrity is called into doubt, now must prove himself.
Beowulf, however, is determined to behave with honor. Since he has heard that Grendel does not fight with weapons, he decides he will face the monster in hand-to-hand combat. Beowulf states,
the monster scorns
in his reckless way to use weapons;
therefore ... I hereby renounce
sword and the shelter of the broad shield,
the heavy war-board: hand-to-hand
is how it will be, a life-and-death
fight with the fiend. Whichever one death fells
must deem it a just judgment by God.
This may also be a practical decision, because the men who have tried to fight Grendel with weapons have not succeeded. Beowulf's statement also shows that he faithful to God, a contrast with the godless Grendel, and is an indication that he has some humility: whatever strengths Beowulf might possess, he knows it is still up to God to decide the outcome of the battle.
Beowulf is brave, resourceful, and confident in his battle with Grendel, which he wins.