Keats began working on his poem "La Belle Dame Sans Merci" in 1819. It consists of 12 quatrains rhymed ABCB. The first three lines of each stanza are written in iambic tetrameter and the fourth line in iambic trimeter. The poem follows the generic conventions of the ballad.

The first feature which makes it typical of Keats' version of romanticism is the nostalgic setting in an idealized version of the Middle Ages, including its appropriation of the folk-poetic form of the ballad. 

Another feature typical of Keats' poetic art is the way that he uses the imagery of nature to establish mood, a technique sometimes known as the "pathetic fallacy." The despair and withering of the knight due to his love for "La Belle Dame Sans Merci" who abandoned him is reflected in the wintry landscape evoked in the final lines:

Though the sedge is withered from the lake,

And no birds sing