Final answer:
Sir Gawain fights the Green Knight to uphold the chivalric code and honor of the Round Table, showing bravery and fulfilling his knightly duty to protect his king and comrades.
Step-by-step explanation:
In Sir Gawain and the Green Knight, Sir Gawain volunteers to fight the Green Knight primarily to protect the honor of his king, King Arthur, and his fellow knights at the Round Table. This action is aligned with the chivalric code of the time, which included principles such as protecting the weak and serving justice. Gawain's decision is not driven by a personal dispute with the Green Knight, the protection of the queen, or a desire to prove the Green Knight's existence, but rather by his sense of duty and honor as a knight in Arthur's court. The choice reflects the ideals of chivalry, where knights were expected to demonstrate bravery and face challenges for the sake of others, especially their liege and peers, embodying the values of their Christianized warrior society.