6.2.2 First conditional
if + present tense | will + infinitive
The first conditional describes a probable future situation. If the condition is fulfilled, the action in the main clause is likely to happen:
If we don't leave soon, we will miss the train.
If you ask him, he will probably help you.
In this type of conditional, the present tenses in the if-clause usually refer to future time and their use is similar to that in future time clauses. Sometimes, however, a present tense in the if-clause can refer to present time:
If you are hungry, you'll find some sandwiches in the fridge.
Compare the zero and the first conditionals:
If I drink too much, I usually get a hangover the following day. (zero conditional to refer to a general situation; one action is always followed by another)
If I drink too much, I will get a hangover tomorrow. (first conditional to refer to one specific future situation)
Present perfect in the first conditional
The present perfect in the if-clause of a sentence in the first conditional emphasises that one action depends on the completion of another:
If I've finished writing my paper by tonight, I'll go out with my friends.
Imperatives in the first conditional
Imperatives can be used to replace either clause of the first conditional:
If you've done the dishes, please mop the floor.
Tidy up your room, and you can go out to play football with your friends.
Modals in the first conditional
Main clause
We can use modals other than will in the main clause of a sentence in the first conditional:
If you ask George, he may/might be able to help you. (possibility)
You can/may leave the room if you've finished the test. (permission)
If he doesn't come soon, we must / will have to leave without him. (obligation)
If you ever go to Chicago, you should take a boat trip on the river. (suggestion)
If you don't watch your steps, you are going to fall over. (prediction)
If-clause
We can use be going to in the if-clause to express intention:
If you are going to speak like that, you'll have to leave.