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 must not help you must not help he must not help we must not help you must not help they must not help
V-ing form
I must not be helping you must not be helping he must not be helping we must not be helping you must not be helping they must not be helping
Perfect
I must not have helped you must not have helped he must not have helped we must not have helped you must not have helped they must not have helped
V-ing perfect
I must not have been helping you must not have been helping he must not have been helping we must not have been helping you must not have been helping they must not 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
must I not help? must you not help? must he not help? must we not help? must you not help? must they not help?
V-ing form
must I not be helping? must you not be helping? must he not be helping? must we not be helping? must you not be helping? must they not be helping?
Perfect
must I not have helped? must you not have helped? must he not have helped? must we not have helped? must you not have helped? must they not have helped?
V-ing perfect
must I not have been helping? must you not have been helping? must he not have been helping? must we not have been helping? must you not have been helping? must they not have been helping?