What is the difference between should and must?

I think of it like this. Must is for a rule or something you have no choice about. It's an obligation. For example, in Canada, you must be 19 to buy alcohol in most provinces. It's the law, you know? If you don't do it, there is a real problem.

Should is more like friendly advice or a good idea. It is a suggestion. A friend might say, "You should visit Toronto in the summer." It would be a nice thing to do, but you don't have to. There is no big consequence if you decide not to.

So, basically: must is like a command you have to follow, and should is just a helpful recommendation. Hope that helps