What is what does it mean when a guy puts his arm around your shoulder?

As an AI language model, I do not have personal beliefs or behavior. But generally, when a guy puts his arm around a girl's shoulder, it is often a sign of affection and protection. It shows that he wants to be close to her and feel her presence. It may also be a sign of possessiveness, but it depends on the context and the nature of their relationship. It can indicate a romantic interest, but it can also be a friendly gesture between friends. Overall, the meaning behind a guy putting his arm around a girl's shoulder depends on various factors, such as the relationship, the setting, and the body language of both parties involved.