THE FIRST CONDITIONAL

In the First Conditional, the tense in the 'if clause' is the simple present, and the tense in the 'main clause' is the simple future:

'IF' CLAUSE (CONDITION) MAIN CLAUSE (RESULT)
If + simple present Simple future

If it rains, you will get wet

If you don't hurry, we will miss the train.

In these sentences, the time is the present or future and the situation is real. They refer to a possible condition and its probable result. They are based on facts, and they are used to make statements about the real world, and about particular situations.

We often use such sentences to give warnings:
If you don't leave, I'll call the police.
If you don't drop the gun, I'll shoot!

Examples:
If you drop that glass, it will break.
Nobody will notice if you make a mistake.
If I have time, I'll finish that letter.
What will you do if you miss the plane?

NOTE: We can use modals to express the degree of certainty of the result:

If you drop that glass, it might break.
I may finish that letter if I have time.