what happens to Ambrosio and Matilda at the end of the story ? Also what things can I say about the book to participate in class?

Ambrosio and Matilda are both in prison. Ambrosio continues to claim his innocence but, when faced with the instruments of torture, falsely confesses his sins. Ambrosia and Matilda are both to burn. Ambrosia signs a contract with Satan (this is never a good idea) to rescue him from prison in exchange for his soul. Lucifer does save him and informs him that Matilda had always been under his charge. Ambrosio dies on some rocks and is damned for eternity.

It really depends on what comes up in your class as far as saying something. A good place to start looking is the GradeSaver themes page below,

http://www.gradesaver.com/the-monk/wikipedia/themes/