You can use the times you want to use the other, because you may have more use options: In the question, MORE is more formal than CAN: Exemplo: May I go to the bathroom? (formal) Can I go to the bathroom? (Normal or informal) And it also has the "modal verb" form, which indicates the probability of something happening, and when you use CAN, you mean that there is a very high possibility of that happening (around 90% chance), and the MAY you say that there is a 50% chance of that happening.I Can go to the Gym I Can drink beer (90%) I May drink beer (50%) Bye!