"The Moon" by Percy Bysshe Shelley is a complicated poem though short. It has both a poetic conceit (i.e., an extended comparison between two things) and an underlying metaphor, which is the metaphor (i.e., comparison of any length between two things) upon which a poem is composed. In stanza one, the conceit is a comparison between the moon and a "dying lady ... / ... / led by the insane ... wanderings of her feeble brain." This is how Shelley perceives and describes the moon as it rises through the atmosphere that varies and veils the appearance of the moon. The underlying metaphor is revealed in stanza two when we learn by inference (i.e., to conclude through a reasoning process) that the poetic speaker--who may or may not be different from Shelley--is comparing his lot in life to his perception of the moon as told in stanza one.
In a pathetic fallacy (i.e., rhetorical device in poems that gives human traits to nature), the speaker asks the personified moon why it is pale and wandering. He asks if it is because the moon is weary "Of climbing heaven ... / ... / Wandering companionless." He asks if it is because it is alone among stars that are of a different kind than it is: "stars that have a different birth, ...." He asks if it is because it is "ever changing." The final line and a half make it clear by inference that it is the speaker himself who feels what is imputed to the moon. He sees the moon as having a "joyless eye" and as finding "no object worth its constancy" when in fact it is the speaker who has a joyless eye because he can find no object worth his devotion and constant love. In other words, he has a broken heart because his lady fair (who is never mentioned) has abandoned him and unworthily withdrawn her love from him.