“Have to” is used in expressing that something is required by rules, duty, or situation. It functions as a verb that is conjugated as “I have to”, “he has to”, “we had to”, “they will have to” in different tenses.
Put “do” or “does” before “have to” to form a question and the negative. For example, “Do you have to go?” “She doesn’t have to talk.”
“Have to” works in present, past, and future.
Present:
She has to eat.
It has to play.
They have to travel.
Past:
He had to send the email.
We had to sing.
Future:
I will have to see.
We will have to try.
Have to vs Must
“Have to” often signifies external rules or requirements.
“Must”, on the other hand, is more an internal obligation, and is more versatile for past and future uses.
“Have to” (or “have got to”) is used for general duties, rules, and necessities.
The negative form “don’t have to” means “not necessary,” and “mustn’t” means “prohibited”.