Conditionals: the first conditional
The form
If + Present Simple, + Will + Infinitive
Will + Infinitive + If + Present Simple (notice that there is no comma in this version)
Very often "if" replaced by words such as: when, until, before, as soon as, after.
After these words we always use Present Simple. Always!
Usage
To talk about real possibilities; something that can actually happen in the future.
Examples
If it rains, I won't go to the park.
If I study today, I'll go to the party tonight.
If I have enough money, I'll buy some new shoes.
She'll miss the bus if she doesn't leave soon.
If I see her, I'll tell her.
If he meets Tom, he'll shout at him.