I must help you must help he must help we must help you must help they must help
V-ing form
I must be helping you must be helping he must be helping we must be helping you must be helping they must be helping
Perfect
I must have helped you must have helped he must have helped we must have helped you must have helped they must have helped
V-ing perfect
I must have been helping you must have been helping he must have been helping we must have been helping you must have been helping they must have been helping
Negation
Simple form
I mustn't help you mustn't help he mustn't help we mustn't help you mustn't help they mustn't help
V-ing form
I mustn't be helping you mustn't be helping he mustn't be helping we mustn't be helping you mustn't be helping they mustn't be helping
Perfect
I mustn't have helped you mustn't have helped he mustn't have helped we mustn't have helped you mustn't have helped they mustn't have helped
V-ing perfect
I mustn't have been helping you mustn't have been helping he mustn't have been helping we mustn't have been helping you mustn't have been helping they mustn't have been helping
Interrogative form
Simple form
must I help? must you help? must he help? must we help? must you help? must they help?
V-ing form
must I be helping? must you be helping? must he be helping? must we be helping? must you be helping? must they be helping?
Perfect
must I have helped? must you have helped? must he have helped? must we have helped? must you have helped? must they have helped?
V-ing perfect
must I have been helping? must you have been helping? must he have been helping? must we have been helping? must you have been helping? must they have been helping?
Interro-negative form
Simple form
mustn't I help? mustn't you help? mustn't he help? mustn't we help? mustn't you help? mustn't they help?
V-ing form
mustn't I be helping? mustn't you be helping? mustn't he be helping? mustn't we be helping? mustn't you be helping? mustn't they be helping?
Perfect
mustn't I have helped? mustn't you have helped? mustn't he have helped? mustn't we have helped? mustn't you have helped? mustn't they have helped?
V-ing perfect
mustn't I have been helping? mustn't you have been helping? mustn't he have been helping? mustn't we have been helping? mustn't you have been helping? mustn't they have been helping?