Overheating is a mechanic that often attempts to simulate realism and prevent players to fire continuously a weapon. The heat temperature of a weapon is shown through a bar and even some graphical effects such as a glowing effect on the weapon or the barrel. when the weapon is overheated many things can happen overheating have different effects from game to game and even from weapon to weapon in the same game.
Most games when weapons are overheated the weapon cease to fire and we are unable to use it during a few seconds, during this time we are vulnerable since we can't return fire and often we are unable to switch weapons until the weapon regains a reasonable temperature.
Some other games can make the weapon malfunctioning, damaging the player, even break or blow up.
While overheating is mostly used to balance machine guns, they are also used for energy weapons when they have no "clip / magazine" and even some silenced machine guns and submachine guns.
In some games when the weapon starts to be hot, but not overheated the bullets can do more damage than if the weapon is cold.
Overheating happens with single barrel machine guns when we fire them continuously, some of them are water cooled or multi barreled to prevent overheating.
When the weapon is overheated we have to change the barrel and replace it with a new one. Machine guns often features quick detachable barrels to make the task easier.
With silenced weapons the silencer might break and can't suppress the sound anymore.