I was looking it up on google and found what in my opinon is the best answer i found.
The apple on the cover of Twilight represents the Forbidden Fruit from the book of Genesis, which symbolizes Bella's and Edward's forbidden love. The cover for New Moon, however, has a lot of opinions. Some think that the single petal dropping off the flower represent Edward leaving Bella, or the single drop of blood Bella bled at her birthday party. On the cover of Eclipse is a torn red ribbon, representing Bella's choice between her love for Edward and her friendship/love for Jacob, and also that Bella is unable to break completely away from her human life. The chess pieces on the cover of Breaking Dawn are a metaphor for Bella-at the start, she is the weakest, the pawn, but at the end of the series, she becomes the strongest, the queen.