Zero Conditional

The zero conditional is used when describing situations which have automatic or habitual results (=general truths). The probability of the result is 100%.

• If you heat ice, it melts." (will melt is also possible)

• If there is a shortage of any product, prices of that product go up.

• My parents get angry if I come home late.

As you can see, both the main clause and the if clause are in the Present Simple.

The zero conditional is often used to give instructions:

• Press the button if you want a receipt.

• If you want to leave a message, speak after the tone.