Primary auxiliary
Am is are
Was were
Shall be will be
Has have had shall have
Does do did sha hill do will do
Modal auxiliary
Can could may might
Must ought to should would used to shall will has to have to shall have to
will have to
Can
Used to denote the ability of the subject to perform an action or to request
permission to perform an action
Could
Used to denote the ability of the subject to perform an action or an offer
made by the subject to perform an action
He could go lonely far away on bicycle.
May
Used to denote the probability of an action taking place or to request
permission to perform an action
It may rain today.
Might
Used to denote the probability of an action taking place or to make
suggestions
Maria might swim whole day.
Will
Used to denote the surety of an action taking place or the assurance of
the subject to perform a particular action
I will study hard tomorrow.
Would
Used to show politeness when requesting or asking if an action can be
done by the subject.
Would you please send me a picture?
Shall
Used to denote the surety of an action taking place or the assurance of
the subject to perform a particular action
Should
Used to denote the necessity of an action to be done by the subject
I should study today to pass tomorrow.
Must
Used to denote the strong obligation or necessity for the subject to do or
not do an action
Students must do homework.
Ought to
Used to denote the obligation of the subject to perform a particular action
I ought to complete homework school days.
Must – have to has to
Used to- habit in past
My father used to go to the gym.
