Do you have to put lava rocks at the bottom of the gas grill for protection of the heat?

No, you don't need to put lava rocks at the bottom of a gas grill for heat protection. Gas grills are designed to operate without them, using burners to distribute heat evenly. However, some people choose to use lava rocks or ceramic briquettes to help retain and distribute heat, enhance flavor, or create a more even cooking surface. Ultimately, it's a matter of personal preference.