Both 'can you' and 'could you' are correct for making requests, but 'could you' is more polite and formal. 'Can you' is suitable for casual situations like talking to friends or family, while 'could you' is better for professional or unfamiliar settings.
'Might' is more commonly used in everyday conversation because it sounds less formal and more natural. 'May' tends to be more polite and formal, making it less frequent in casual speech.
'Should' is used to ask for or give advice, often in close or personal situations. For example, 'What should I do?' or 'I think you should...' are common patterns. Including 'I think' softens the advice, making it more polite.
'Shall we' is a polite way to suggest doing something together, like 'Shall we dance?' or 'Shall we go for a drink?' 'Will we' is used to ask about future plans, such as 'Will we have to pay for this later?' They are not interchangeable.
'Were' is used in 'If I were you' because it refers to an unreal or hypothetical situation. 'Was' is used for possible past situations, but 'were' is correct for present unreal conditions like giving advice.
'Must' is rarely used in everyday conversation because it sounds very strong. It is more common in official rules or serious advice, such as 'You must not smoke here' or 'You must stop eating junk food.'
'Must not be' expresses a high likelihood that something is not true. For example, 'This must not be the right place' suggests there is a strong chance the location is incorrect.
'Can't be' expresses complete impossibility, while 'must not be' suggests a very low chance something is true. For example, 'That can't be Risa' means it is impossible, whereas 'That must not be Risa' implies it is unlikely.
After 'should' in advice patterns, the verb should be in the infinitive form. For example, 'We shouldn't eat' or 'We shouldn't forget.' Using 'ing' or past tense forms is incorrect.