The zero conditional is often used:
If you start with the if clause then you need to separate it from the main clause with a comma.
If Clause | Comma | Main Clause |
If + Present Simple | , | Present Simple |
If you start the sentence with the main clause you must not separate it from the If clause with a comma.
Main Clause | If Clause |
Present Simple | If + Present Simple |
Examples:
If Clause | Comma | Main Clause |
If + Present Simple | , | Present Simple |
If this happens | , | that thing happens. |
If you heat ice | , | it melts |
Main Clause | If Clause |
Present Simple | if + Present Simple |
That thing happens | if this happens. |
Ice melts | if you heat it. |
The grass gets wet | if it rains |