I must butter you must butter he must butter we must butter you must butter they must butter
V-ing form
I must be buttering you must be buttering he must be buttering we must be buttering you must be buttering they must be buttering
Perfect
I must have buttered you must have buttered he must have buttered we must have buttered you must have buttered they must have buttered
V-ing perfect
I must have been buttering you must have been buttering he must have been buttering we must have been buttering you must have been buttering they must have been buttering
Negation
Simple form
I must not butter you must not butter he must not butter we must not butter you must not butter they must not butter
V-ing form
I must not be buttering you must not be buttering he must not be buttering we must not be buttering you must not be buttering they must not be buttering
Perfect
I must not have buttered you must not have buttered he must not have buttered we must not have buttered you must not have buttered they must not have buttered
V-ing perfect
I must not have been buttering you must not have been buttering he must not have been buttering we must not have been buttering you must not have been buttering they must not have been buttering
Interrogative form
Simple form
must I butter? must you butter? must he butter? must we butter? must you butter? must they butter?
V-ing form
must I be buttering? must you be buttering? must he be buttering? must we be buttering? must you be buttering? must they be buttering?
Perfect
must I have buttered? must you have buttered? must he have buttered? must we have buttered? must you have buttered? must they have buttered?
V-ing perfect
must I have been buttering? must you have been buttering? must he have been buttering? must we have been buttering? must you have been buttering? must they have been buttering?
Interro-negative form
Simple form
must I not butter? must you not butter? must he not butter? must we not butter? must you not butter? must they not butter?
V-ing form
must I not be buttering? must you not be buttering? must he not be buttering? must we not be buttering? must you not be buttering? must they not be buttering?
Perfect
must I not have buttered? must you not have buttered? must he not have buttered? must we not have buttered? must you not have buttered? must they not have buttered?
V-ing perfect
must I not have been buttering? must you not have been buttering? must he not have been buttering? must we not have been buttering? must you not have been buttering? must they not have been buttering?