Technically, "The Wife of Bath's Tale" is a Breton lai, which is a short romance that features knights, noble ladies and supernatural incidents. This kind of tale originated in a northeastern part of France called Brittany, hence the adjective "Breton" to describe it. The Wife signals that we're about to encounter a story of this genre when she describes King Arthur as he "of which that the Britons speken greet honour" (864, emphasis ours), and goes on to fulfill the conventions of the genre.
In the bigger picture (by which we mean, outside the tiny group of scholars who study this stuff full-time) "The Wife of Bath's Tale" is part of the quest genre. A protagonist is missing something (the answer to the queen's question) that he must travel near and far to find, encountering trials and tribulations along the way. Although the trials and tribulations our knight suffers don't amount to much more than the fact that women, being individuals, all desire different things, the loathly lady he meets at the end of the quest could qualify as a monster. Consider: she's very, very ugly, and despite helping him to answer the queen's question, she also prevents the knight from reaching what we presume is his other goal, marriage to a suitable young damsel. Like the protagonist of any quest, the knight is only able to "vanquish" the monster once he shows inner growth – in our knight's case, a sensitivity to women's desires.