The symbolism of the moon is very important for the Creature in Mary Shelley's novel Frankenstein. Upon first opening his eyes, as denoted in chapter eleven, the Creature is frightened by the light. Given that the light burns the eyes of the Creature, he closes them. After closing his eyes, the Creature is frightened by darkness. At this point, it seems that the Creature can find no happy medium between day and night (given daylight huts his eyes and makes him too hot and night brings complete darkness).
Later, the moon comes out.
Soon a gentle light stole over the heavens, and gave me a sensation of pleasure. I started up, and beheld a radiant form rise from among the trees.
For the Creature, the moon is the first thing which brings him pleasure. It lights the darkness and allows him to travel without being too hot (as brought on by the heat of the sun).
Later, in the same paragraph, the creature goes on to describe how important the moon is given it is the only thing which brings him pleasure.
The only object that I could distinguish was the bright moon, and I fixed my eyes on that with pleasure.
Therefore, the moon is important for it is the only thing which brings the Creature pleasure. Given he has been abandoned by Victor, pleasure for the Creature comes sparingly.
Given the "bond" the Creature has with the moon, each time he is seen by Victor it is during moonlit nights. The Creature is seen in the shadows thrown by the light of the moon. The moon exists as a symbol of the Creature.
The moon is also often known as a feminim figure. This emphasises the lack of women in Frankenstein's creation as he makes an artifical creation (themes of Romanticism and also masturbation). Therefore the moon is representative of women's absence in this creation and the failure in this creation portrays the wrongness of this method of creation.
The moon creates a gothic mood in the story Frankenstein. It is also very closely tied to the monster. When the monster is close the moon shines bright. The moon almost acts as a warning that the monster is near or something is about to happen. For example, prior to Elizabeth being murdered the author describes the moons presence. It is as if the moon shining was bringing our attention to the fact that the monster was about to murder Elizabeth. This is just one of many examples that lets the reader know that the monster is going to appear soon.