Wah How to use first conditional.

We use first conditional when we talk about actions in the future that are not happening now but are likely to happen in the normal turn of events.

We use If + present simple tense to talk about the possible future condition.
We use will + verb to talk about the possible future result. 
    If it rains tomorrow, I will stay at home.
    If he spends all his money, he won't be able to buy a new car.
    If you feel better tomorrow, Will you go to the sea?

First conditional sentences are normally reversible.
    I will stay at home if it rains tomorrow.
    He won't be able to buy a new car if he spends all his money.
    Will you go to the sea if you feel better tomorrow?

We can use going to for the events that are going to happen.
    If you don't hold that handrail, you are going to fall off.
    You are going to get wet if you run through the rain.
    If she doesn't stop eating junk food and sitting all day, she is going to be fat for her favorite dresses.

Note: We can use can, may instead of using will.
    If you study hard right now, you can easily pass the examination.
    I may help you if you beg me. 

We can play rainwater if it rains this afternoon.

Wah How to use May / Might as well.

We know how to use may and might in this topic:

Wah How to use "May and Might"

We use May / Might as well + Verb to give suggestions like should, ought to but we usually use this form when you think there is no choice or nothing better to do. 
We often use it when you are not eager about that suggestion.

• There isn't anything to do and I feel a little drowsy. I might as well go to bed now.
• Here comes a bus. We might as well take it. We are already late.
• There is nothing on TV this morning. we might as well watch the comedy.
• You cannot leave before 10.00 A.M., You may as well wait here.
• I am free now, I may as well go shopping with you.
• I have finished all my work. I may as well go home now.
• You might as well tell her the truth. Lying will make everything worse.

Wah How to use "May and Might"

May and Might are the auxiliary verbs as are should,ought to and will. Let's see how to use them.

We use May when we are asking for permission.
    May I come in please? 
    May I borrow your bicycle this afternoon? 
    May I sit here please?
    You mayn't may not leave until you finish your work.
    You may not smoke in here.

We use May when you are not sure or to talk about the possibility of something.
    It may rain today. It mays to rain. is incorrect.
    I may go to the United States next month if it's possible.
    There may be a lot of cars on the road right now.
    I'm so busy today, I may not have time to work out.

Wah How to use "Must/Might/May/Can't be"

When you are sure something is true, you can say "must be". 
        He is speaking Japanese, He must be Japanese. (I am sure he is Japanese.)
        She must be a police officer.(I think she is a police officer.)
        This must be the way to the park. (I am certain this is the way to the park.)

If you are quite sure something may be true, you can say "may/might be".
        He is so late at the meeting, the traffic might be bad.
        John is not at the office now, he may be taking the day off.
        I am not sure but she might be older than me.

And If you want to say something you think it is unlikely, you can say "can't be".
        He is very old, he can't be the student.
        Sarah is at the hospital, she can't be working today.
        This restaurant is very delicious, it can't be going out of business.

Kenny Chesney - Must Be Something I Missed
"There must be something I missed
I wake up in the morning just making a fist
I don't call it living, I just exist
There must be something I missed..."