The Green Knight is a very ambiguous character. When he shows up at Arthur's hall, he is a forbidding figure. His size, strength, and obvious wealth are a challenge to Arthur's prestige. His challenge, which is not to fight but to endure a single blow, is also a comment on "knightly play" and the effectiveness of Arthur's knights. The Green Knight comes off as arrogant and superior. When Gawain decapitates him but he does not die, the Green Knight transforms into a supernatural figure. He seems to be invulnerable.

These aspects suggest that the Green Knight represents a power that is outside and greater than Arthur's, one that serves as a check on Arthur's hubris. In fact, readers often associate the Green Knight with some sort of nature god, seeing his decapitation and renewal as emblematic of the seasons. In this sense, he represents a kind of competing belief system to Christianity.

Gawain may be the purest and best of Arthur's knights, but he knows he is no match for the Green Knight. His quest to honor his pledge and seek the Green Knight to take a return blow is a test of his virtue. This is borne out by Gawain's experience with Bertilak and his wife: the real test for Gawain is his ability to maintain his knightly virtue in the face of temptation. In that sense, we can see the Green Knight/Bertilak as a kind of trickster or, even, a figuration of Satan, since, like Satan, he tempts the Christlike Gawain. Unlike Satan, however, the Green Knight does not take advantage of his power to kill Gawain; his test has been to confirm Gawain's purity and integrity, not undermine it. So, in that sense, he is a "good" character.