If + present + will + verb
First conditional is used to talk about actions/events in the future which are likely to happen or have a real possibility of happening.
- If it rains tomorrow, I’ll stay at home.
- If my father doesn’t buy me a bike for my birthday, I will be very unhappy.
(I think there is a real possibility of rain tomorrow. In this condition, I will stay at home)
(I think there is a real possibility that my father won’t buy me a bike. In this condition, I will be unhappy)
Other modal verbs can be used in place of WILL.
- If it’s sunny tomorrow, I might go to the beach. (going to the beach is only a possibility)
- If you come early, you can meet my mother. (it is possible for you to meet my mother)