Answer:
The main theme of "The Necklace" a contrast between greed and generosity. Madame Loisel, the protagonist, lives a modest, yet comfortable middle class life with her husband. However, she feels that her lack of luxury is a very great injustice. Her life is comfortable enough to afford one servant, but she wishes for several. She has plenty of food, but she dreams of "delicate meals." Her husband can barely afford to buy her a ball gown, but she insists on having jewelry to go with it. When she first sees her friend's diamond necklace, "her heart [beats] covetously." Her greed stands in marked contrast to the generosity of her husband and Madame Forestier.
The necklace itself represents the theme of appearances versus reality. While sufficiently beautiful to make Madame Loisel feel comfortable during the ministerial ball, the necklace is actually nothing more than paste and gilt. Thus, it is not the reality of wealth or high social class that is important for Madame Loisel, just the appearance of it.
