Take a story's temperature by studying its tone. Is it hopeful? Cynical? Snarky? Playful?
Formal, Laudatory, Pious, Mournful
The narrator of Beowulf uses several different tones over the course of this long epic poem, but throughout everything he is always formal. This isn't a chummy, chatty, nudge-you-in-the-ribs kind of narrator. Instead, everything in Beowulf seems to be spoken with grave, calm, even stiff formality. We see this in the characters as well as in the narrator; even Beowulf himself announces his own name through an elaborate speech about his deeds.
Although his tone is always formal, the narrator of Beowulf does shift between three more specific tones, depending on what's happening at the moment in the story. When Beowulf or someone else is behaving especially heroically, the narrator becomes laudatory, or praising. In fact, we'd go so far as to say that this narrator does some real boot-licking. To listen to the narrator, you'd think that Beowulf was just the most awesome, honorable, powerful hero who ever lived – which is exactly what epics are supposed to be about. But when Beowulf starts losing, the narrator becomes mournful, lamenting the hero's defeat and the suffering of the people, or pious, reminding us that all heroism is dependent on God's favor.