This conditional is used when the result will always happen.
If + present simple, .... present simple.
1. If I miss the 8 o'clock bus, I am late for work.
2. If you heat ice, does it melt?
3. If people don't eat, they get hungry.
4. If I am late for work, my boss gets angry.
5. If I work too much, I get tired.
It's used to talk about things which might happen in the future. Of course, we can't know what will happen in the future, but this describes possible things, which could easily come true.
if + present simple, ... will + infinitive
1. If it rains, I won't go to the park.
2. If I study today, I'll go to the party tonight.
3. If I have enough money, I'll buy some new shoes.
4. She'll be late if the train is delayed.
5. She'll miss the bus if she doesn't leave soon.
We can use it to talk about things in the future that are probably not going to be true. Also, we can use it to talk about something in the present which is impossible, because it's not true.
if + past simple, ...would + infinitive
1. If I won the lottery, I would buy a big house.
2. If I met the Queen of England, I would say hello.
3. She would travel all over the world if she were rich.
4. If I had his number, I would call him.
5. If I were you, I wouldn't go out with that man.
It talks about the past. It's used to describe a situation that didn't happen, and to imagine the result of this situation.
if + past perfect, ...would + have + past participle
1. If she had studied, she would have passed the exam.
2. He would have been on time for the interview if he had left the house at nine.
3. If we had taken a taxi, we wouldn't have missed the plane.
4. She wouldn't have been tired if she had gone to bed earlier.
5. She would have become a teacher if she had gone to university.