Conditionals Part 1

or if-sentences
A.
How do you talk about things which are always true? For example, every time I tell my boyfriend to wash the dishes, it turns out he had to work overtime. But every single time! Here is how to express that with a conditional sentence:
If I tell my boyfriend to wash the dishes, he has to work overtime.

This is the so-called "zero" conditional. Every time something happens, something else happens. We use present tenses for that.

Question: Can we use past tenses?
Answer: Yes. If both the condition and the result are in the past. For example:
When I was at school, if my history teacher as much as looked at me, I forgot everything, even my own name.
And that is true, she scared the hell out of me. I hated history, partly because of her. I tried to study, I did my best. And I could even recite the lesson before class. The moment she was inside the classroom, nothing comprehensible came out of my mouth. I got good grades usually, but not in history... So there. This was always true. In the past. So I used past simple.

B.
Let's look at a different situation. Let's say I want to do something and I wonder what the result of it will be. How do we say that?
Do you remember how in the cartoon "Dexter's Lab" Dee Dee, his sister, kept going into his laboratory and when she saw a big red button, she always said innocently: "What does this button do?". And before Dexter could say anything, she pushed it and the lab exploded. Well, I guess we can say:
What will happen if I Dee Dee pushes the button?
If she pushes the button, the lab will explode.

You can see that after "if" we use present simple tense, and in the other part of the sentence, it is the future with "will". This is one of the most common cases of "first" conditional.
First conditional is real. The situation we talk about is likely to happen. We use present tenses after "if".
Another example can be,
If it rains tomorrow, I will take the bus to work.
You see, I normally walk. It is 20 minutes from where I live and it is good exercise in the morning.But it becomes a very unpleasant experience if I have to walk in the rain. So if it rains, I will most probably take the bus so I don't get all wet.

Question: can we use other tenses?
Answer: Yes, of course, anything that makes sense. As long as you keep to the "present after if - modal verb and infinitive in the other clause" scenario.
Here is an example:
If my husband has done the housework when I get home, later tonight I can strip for his to reward him for it.

And with this image in your head, ladies and gentlemen, I end part 1 of Conditionals.