I think the Irregular Verb "To Be" is the most important verb in the English language, but if it isn't, then the irregular verb "To Have" is. Learn them both very well!

 

 
IRREGULAR VERB   "TO HAVE"
to have
Present Present Past Past
Progressive Progressive
I
have am having had was having
You
have are having had were having
She, he, it
has is having had was having
We
have are having had were having
They
have are having had were having
Present Past Future Future Conditional
Perfect Perfect using to go
I
have had had had will have am going to have would have
You
have had had had will have are going to have would have
She, he, it
has had had had will have is going to have would have
We
have had had had will have are going to have would have
They
have had had had will have are going to have would have