1. We use the first conditional to talk about actions or events in the future which are likely to happen or have a real possibility of happening.

2. If it rains tomorrow, I will stay at home.
I think there is a real possibility of rain tomorrow. In this condition, I will 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 that my father won't buy me a bike. In this condition, I will be unhappy

3. FORM IF condition result present simple WILL + base verb If it rains
I will stay at home.

4. Also, sometimes….
the conditional clause is in the present or past tense and refers to a state or event in the past. The result can be in the past, present, or future.

5. If she took that flight yesterday, she arrived at 10pm.
If she took that flight yesterday, she is somewhere in town today.
If she took that flight yesterday, we'll see her tomorrow.

6. And there’s also…
A condition clause (protasis) in the present tense refers to a future event, a current event which may be true or untrue, or an event which could be verified in the future. The result can be in the past, present, or future:

7. Examples
If it's raining here now, then it was raining on the West Coast this morning.
If it's raining now, then your laundry is getting wet.
If it's raining now, there will be mushrooms to pick next week.
If it rains this afternoon, then yesterday's weather forecast was wrong.
If it rains this afternoon, your garden party is doomed.
If it rains this afternoon, everybody will stay home.
If I become President, I'll lower taxes.

8. Possible variations of the basic form
Sometimes instead of if + present + future, we may have:
a) if  + present + may/might (possibility)
If the climate keeps warming, the Arctic might be warm enough for swimming.
b) if + present + may (permission) or can (permission or ability)
If your documents are in order, you may/can leave at once. (permission)
If it stops raining, we can go out." (permission or ability)
c) if + present + must, should or any expression of command, request or advice
if you want to look slim, you must/should eat less meat.
if you want to look slim, you had better eat less meat.
if you want to look slim,  eat less meat.

9. We can use other modal verbs in place of will.
Important points
We can use other modal verbs in place of will.
If it is sunny tomorrow, I might go to the beach. going to the beach is only a possibility
If you come early, you can see my mother before she leaves. It is possible for you to see my mother

10. The two clauses are inter-changable
If I have enough money,
conditional clause    
I will go to Japan.    
 main clause
I will go to Japan,
main clause    
if I have enough money     
conditional clause

11. Instead of if + present tense, we can have:
a) if + present continuous, to indicate a present actions or a future arrangement."
If you are waiting for a bus (present action), you'd better join the queue.
If you are looking for Peter, you'll find him  upstairs.
If you're staying for another night (future arrangement), I'll ask the manager to give you a better room.
b) if + present perfect
if you have finished dinner, I'll ask the waiter for the bill.
If has written the letter, I'll post it.
If they haven't seen the museum, we'd better go there today.

12. Certain modal auxiliary verbs (mainly will, may, might, and could) are not usually used in the condition clause (protasis) in English:

13. *If it will rain this afternoon, …
*If it may have rained yesterday, …
This is the problem for Hebrew speakers!!

14. There are exceptions, however, in which will is used exactly as in the first example, namely when the action in the if clause takes place after that in the main clause:
(The weather forecast says it's going to rain.) Well, if it will rain, we must take umbrellas.
If aspirins will cure it, I'll [I will] take a couple tonight instead of this horrible medicine.

15. Other situations in which will can be used in an if clause include when will is not being used as an auxiliary verb, in other words when it is being used modally to express willingness, persistence, or a wish:
If you'll [you will] just hold the door open for me a moment, I can take this table out to the kitchen.
If you will keep all the windows shut, of course you'll get headaches.
If you will excuse me, I think I will slip into something more comfortable

16. In colloquial English, the imperative is sometimes used to form a conditional sentence: e.g. "go eastwards a mile and you'll see it" means "if you go eastwards a mile, you will see it".

17. Issues to think about
Problems for Hebrew speakers: translate and discover
Problem of the comma
Incremental presentations.

18. Ideas for teaching Songs and stories where it is a repeated structure
Superstitions
Giving advice
Emergency procedures
Chain stories