Во-первых,модАльные глаголы. Это те глаголы,что связывают указательные предложения.
Can`t have:
1. You can`t have your cigarettes at your bag.
2. You can`t have a dirty mind, during the exam.
3. You can`t have it, while it`s not appropriate.
Must have:
1. You must a have clear identification, while you are having a speech.
2. You must have your own words, otherwice that`s a pragiarism in that context.
3. You must have the food out there, unless you don`t want it.