Obligation in the present:
- I have to finish my work before this evening.
- I have got to learn English if I want to live in the USA.
- I must see the doctor soon because I don’t feel well.
- It is obligatory that I stop when the traffic light turn red.
- It is necessary that I take a taxi. I’m late.
Obligation in the past:
- I had to work extra hours to pay my bills.
Obligation in the future:
- I’ll have to borrow money.