Both Beowulf in Beowulf and Sir Gawain in Sir Gawain and the Green Knight go on a perilous journey or quest that tests their mettle. Beowulf travels with his men to Heorot to kill the monster Grendel, who has been terrorizing the Danish mead hall. This monster has been unconquerable. Gawain travels to the Green Chapel to meet what he thinks will be his certain death. Gawain had struck off the head of the Green Knight the year before and had promised, should the Green Knight survive, that he would show up a year and a day later to receive a similar blow. Unbeknownst to Gawain when he chops off the Green Knight's head, the Green Knight, under enchantment, has the power to reattach it.

In both cases, a knight leaves the comforts of home out of a sense of chivalry to face a deadly foe. However, while Beowulf makes this choice freely, Gawain is responding to an obligation. He has made a promise and, as a knight of King Arthur's court, has no choice but to be true to his word.

Both knights are alike in that they survive their initial test: Beowulf kills Grendel, and Sir Gawain's life is spared. However, while Beowulf does a positive good for his community in that he rids human civilization of a monster trying to disrupt it at its core, Sir Gawain, in contrast, saves only himself. His story is about how he faces his own personal temptation to lie to protect his life when he accepts and keeps secret—in violation of a promise to his host—a green belt or girdle that is supposed to safeguard him from being killed.

While Gawain's life is spared, he has to face the reality of his own weakness and imperfection. Beowulf, in contrast, is rewarded and esteemed as a hero for defeating Grendel and later Grendel's mother. He will be killed in his old age when he slays a dragon, but his life is more firmly in the heroic mold than Sir Gawain's.

Both works are deeply imbedded in a Christian tradition. Beowulf can be seen as representing the Christian's fight against evil. Grendel is seen as descendant of Cain, marked by the devil, and is characterized by his rejection of civilized norms—for example, his embrace of cannibalism. Sir Gawain's chivalry is placed within a Christian context: he prays to the Virgin Mary for protection, and the pentangle he wears is a Christian symbol helping to remind him of Christ's suffering on the cross and the virtues he, Gawain, aspires to. If Beowulf has to fight his temptation to pride, a deadly sin, Gawain has to fight his desire for self-preservation, and learns humility in the process.