I am not a native English speaker, so I don't know if my answer is 100% accurate. Maybe someone else will explain it better :) "Should" and "ought to" should be almost the same, don't worry about them. "Should" is used more often. "Must" and "have to" are also very similar. There is only a small difference: "Must" means something you do because you want to, "Have to" means something you do because something forces you to. Example: A mother and a son go to the church every Sunday. The mother is a Christian, but the son hates the church and only goes there because his mother tells him to. The mother MUST go to church, but the son HAS TO go to church. More examples: "I must study every day." I believe it helps me, and I decide to study every day because I want to improve. "I have to study every day." There are lots of hard tests, I will fail if I don't study. Also, you can use "must" to talk about assumptions. "You are an actor? That must be a fun job!" This means: "I don't know if it is a fun job, but I assume it is!". "May" and "might" are very similar, but there is a small difference in probability. "This may happen." - Normal. "This might happen." - I think it will not happen. The probability is under 50%. Also, people often use "can" instead of "may", it sounds more modern. Hope this helps! 頑張ってねぇ！