I must head you must head he must head we must head you must head they must head
V-ing form
I must be heading you must be heading he must be heading we must be heading you must be heading they must be heading
Perfect
I must have headed you must have headed he must have headed we must have headed you must have headed they must have headed
V-ing perfect
I must have been heading you must have been heading he must have been heading we must have been heading you must have been heading they must have been heading
Negation
Simple form
I must not head you must not head he must not head we must not head you must not head they must not head
V-ing form
I must not be heading you must not be heading he must not be heading we must not be heading you must not be heading they must not be heading
Perfect
I must not have headed you must not have headed he must not have headed we must not have headed you must not have headed they must not have headed
V-ing perfect
I must not have been heading you must not have been heading he must not have been heading we must not have been heading you must not have been heading they must not have been heading
Interrogative form
Simple form
must I head? must you head? must he head? must we head? must you head? must they head?
V-ing form
must I be heading? must you be heading? must he be heading? must we be heading? must you be heading? must they be heading?
Perfect
must I have headed? must you have headed? must he have headed? must we have headed? must you have headed? must they have headed?
V-ing perfect
must I have been heading? must you have been heading? must he have been heading? must we have been heading? must you have been heading? must they have been heading?
Interro-negative form
Simple form
must I not head? must you not head? must he not head? must we not head? must you not head? must they not head?
V-ing form
must I not be heading? must you not be heading? must he not be heading? must we not be heading? must you not be heading? must they not be heading?
Perfect
must I not have headed? must you not have headed? must he not have headed? must we not have headed? must you not have headed? must they not have headed?
V-ing perfect
must I not have been heading? must you not have been heading? must he not have been heading? must we not have been heading? must you not have been heading? must they not have been heading?