What is my boyfriend turns into a different person when he drinks?

As an AI language model, I do not have any information about your personal life or relationship. However, it is a common phenomenon that alcohol can change a person's behavior and personality. Some people may become more outgoing, while others may become aggressive or moody. If you are concerned about your boyfriend's behavior when he drinks, it might be a good idea to talk to him about it when he is sober. You could express your concerns and discuss ways to address the problem together. It may also be helpful to encourage him to seek professional help or support from a therapist or support group if necessary.