When we are thinking about facts, they are generally true, we use:
If + Present tense + Present tense
Examples:
- If it rains, you get wet.
- If you don't eat, you get hungry.
- If it snows, the air is cold.
In the examples above, notice how we use a comma after the "if" clause. The comma is always placed after the "if" clause.
Present tense + If + Present tense
Examples:
- The house shakes if there's an earthquake.
- Batteries can't charge if there's no electricity.
- Plants die if you don't water them.
The comma is not needed in this form.