In this type 1 first conditional, the simple present tense is used in the if-clause, and the tense in the main clause is the simple future tense.

'If' Clause Main Clause
If + simple present tense Simple future tense
If you leave now, you'll arrive home early.

 

This conditional shows the outcome (you’ll arrive home early) if the condition is fulfilled (if you leave now). We use this conditional when the situation in the if-clause appears likely or there is a possibility of it happening.

 

We can turn the two clauses the other way round so that their positions are reversed as follow:

Simple future tense if + simple present tense
You'll arrive home early, if you leave now.

Whether the 
if-clause or the main clause comes earlier, both are acceptable.
 
 

The first conditional sets up a present condition and a probable future outcome.

Examples:

  • If you go with me, I will pay for your fare.
    (If the condition in the if-clause is fulfilled, the action in the second clause will happen, that is I will pay for your fare.)
  • If I see him tomorrow, I will tell him the good news.
  • If the weather remains fine, we will go to the beach.
  • If you continue to feel better, you will be out of the hospital soon.

 

 

We may use going to in the first conditional to refer to a future event.

Examples:

  • If she passes her driving test, we are going to celebrate at a good restaurant. 
  • If you don’t hurry, we are going to be blacklisted for being late.

 

 

First conditional and modal verb. 

Modal verbs may be used in the first conditional. The modal verbs have a future meaning and so are used instead of the future tense in the main clause, not in the conditional clause.

  

Conditional Clause Main Clause
If + simple present tense can/could; will/would; may/might; shall/should
If the weather improves, we will go to the park.

 

  

The modal verbs are used in type 1 conditional sentences to express willingness, possibility, permission, and suggestion.

Examples:

  • If the movie is boring, we can always leave. (Willingness)
  • If you help me with this, I could finish it earlier. (Probability)
  • If she is angry with you, I would ask her why.  
  • If you are in a hurry, you may leave now. (Permission)
  • If we save enough money, we might visit you next year.  
  • If he drives faster, we shall arrive there before dark. (Possibility)
  • If we want to get there on time, we should take a taxi. (Suggestion)