In Beowulf, the characteristics of loyalty and bravery are as much a part of the characters as the they are of the story. Beowulf's story was passed through generations and between cultures in the oral tradition. Generally a scop (or skald) would share the tale; it was one of the few forms of entertainment available to people at that time.
What made the scop's story so engaging was the manner in which it was told: with excitement. More importantly he would have described characters the audience would have admired: both loyal and brave.
Beowulf and Wiglaf are such men. Beowulf is mindful to bring glory to Hygelac, his feudal lord.
Hrothgar, King of the Danes, has built a "master mead house" that he names Heorot. Grendel (the monster) hears sounds of celebration:
Then an evil creature who dwelt in darkness, full of envy and anger, was tormented by the hall's jubilant revel day by day...
And so Grendel attacks the mead hall repeatedly, killing many people for twelve years. The language of the storyteller is beautiful:
Still did the evil one, the dark death-shadow, lie in wait for old and young alike, prowling about and lurking at night on the misty moors...
As the character of the evil one is developed, so too is that of the hero. The story continues: when Beowulf hears these sad stories, he sets out to offer his services. However, to heighten the suspense, the storyteller does not at first reveal his identity. His characteristics speak for him first:
...he was the mightiest man of valor—stalwart and noble
When Beowulf arrives and is challenged by the lookout, he gives his credentials: the names of those he has descended from and their deeds. At the hall, the Geats are met by Wulfgar, the Wendel chief. He recognizes Beowulf's bravery noting that the Geats are men of "courageous valor," not "exiles." His loyalty is evident in protecting Hrothgar from these strangers.
As Beowulf prepares for Grendel's arrival, he puts aside his sword. His bravery is obvious when he says:
I reckon myself to be in the ready for grim deeds of war, and in no way weaker than Grendel. For this reason will I not give his life to the sleep of death with a sword...He has no skill to strike me with sword...mighty though he may be in his horrific feats. We shall both spurn the sword this night...and make war without weapons.
The bravery of Beowulf's men is seen as well—even while certain they will die, they do not run, but lay down to rest:
None thought their steps would ever go thence back to the people and the fortresses that fostered them, to the lands they loved.
In battle, Beowulf tears Grendel's arm from him, which will lead to his death. Soon, his mother appears to avenge his death, killing and taking one of Hrothgar's dearest "chieftains." Without a second thought, Beowulf sets out again with bravery to vanquish Grendel's dam (mother). They battle fiercy, but Beowulf is once again victorious.
Many years pass and Beowulf becomes King. A dragon is terrorizing his land, so he sets out with men to kill "the murderous monster."
In battle, Beowulf—fifty years after killing Grendel—is not as strong. He is beset upon by the dragon, but Wiglaf, showing loyalty to his king and bravery, goes to his aid when others flee.
[Wiglaf] did not hesitate, but seized the yellow linden of his shield and drew a sword...
Beowulf, dying, hands over his leadership to the last surviving member of his line. In all of this, the characters show bravery and loyalty.