1. Similarities
1.1. Speculate and deduce thing about the present or past
1.2. Uses
1.2.1. Must
1.2.1.1. Certain that something is true
1.2.2. Might/May/Could
1.2.2.1. It's possible something is true, but we aren't certain
1.2.3. Mustn't/Can't
1.2.3.1. Certain that something is not true
1.2.4. Mightn't/May not/ Couldn't
1.2.4.1. It's possible something is not true
2. Examples
2.1. Must/Mustn't
2.1.1. She must be studying for pase the exam
2.1.2. He mustn't say lies
2.1.3. They must have learned english in the college
2.1.4. She can't be speaking all the class
2.2. Might (not)/May/(not)/Could(not)
2.2.1. You could be and excellent dancer
2.2.2. He might not drink to much coffee
2.2.3. She may have gone to the gym
3. Differences
3.1. Form
3.1.1. Present situations
3.1.1.1. Affirmative
3.1.1.1.1. Must/Might/May/Could/Can + Subject pronoun+ inifinitive or be+-ing
3.1.1.2. Interrogative
3.1.1.2.1. Must/Might/May/Could/Can + Subject pronoun+ infinitive?
3.1.1.3. Negative
3.1.1.3.1. Mustn't/Mightn't/May not/Couldn't/Can't + Subject pronoun+ infinitive or be+-ing
3.1.2. Past situations
3.1.2.1. Affirmative
3.1.2.1.1. Must/Might/May/Could/Can + Subject pronoun+ past participle
3.1.2.2. Negative
3.1.2.2.1. Mustn't/Mightn't/May not/Couldn't/Can't + Subject pronoun+ past participle
3.1.2.3. Interrogative
3.1.2.3.1. Must/Might/May/Could/Can + Subject pronoun+have+ participle?