loop issue

I am using a sensor to detect something. When something is detected, the signal becomes high in Arduino. Here, I have some problems in coding. I do not want the Arduino to do anything when the signal is low, and started to work when the signal is high. How can I stop looping the code (because the loop run automatically in Arduino) when the signal is low:

if (signal == LOW) { WHAT CODE SHOULD I PUT HERE } if (signal == HIGH) { start to work; }

https://www.arduino.cc/en/Reference/Else

Hint: If signal is not LOW it has to be HIGH.