What Will Happen?
Zero Conditional
Use the zero conditional if an action always occurs as the result of another action. The zero conditional is used to express conditions that are always true.
Example:
"If I eat fried foods, my stomach gets upset."
Tom sneezes if he works with spices.
The present simple is used in both the 'if' clause and the result clause.
'If' clause - present simple + , + result clause - present simple
"If I eat fried foods, my stomach gets upset."
Tom sneezes if he works with spices.
Do not use a comma, when placing the result clause first.
The police clear public areas of people if the president is going to speak.
First Conditional
Use the first, or 'real', conditional if an action will occur if something happens. The first conditional is used when a result is realistically possible.
'If' clause - present simple + , + result clause - future with will
The food cost invoices will arrive on Monday if we mail them tonight.
"If she makes reservations today, her room will ready on Tuesday."
Do not use a comma, when placing the result clause first.
We will find lodging if a local points us in the right direction.
'Unless' is also used in the first conditional to mean 'if not'.
If he doesn't come soon, we won't go to lunch = Unless he comes, we won't go to lunch.
Use of 'May' and 'Might' in the First Conditional
When a future result is not certain based on a condition, use 'may' or 'might'.
'If' clause - present simple + , + result clause - 'may / might' + verb
Security will tighten if there is another terrorist attack.
The front desk personnel will provide excellent customer service if we pay them well.