Heavy Grunts are high Covenant military Grunts which are deployed to use of heavy weaponry, turrets and small vehicles.
Heavies are often found operating as heavy support units and usually operate heavy weapon systems such as Plasma Cannons, Shade Turrets and Fuel Rod Guns with deadly effect. During the Fall of Reach, Heavies are usually seen operating plasma turrets on Wraiths. They will not usually retreat from their position unless if their out of range or too close to use it, then they will pull out Plasma Pistols to act as a standard Grunt and fire at the player. Unlike most Grunts, Heavies rarely throw Plasma Grenades nor suicidal attack. In Halo 2, Heavies usually carry and man Plasma Cannons. On Halo 3, Heavies are usually deployed in Covenant Watch Towers to fire with Fuel Rod Guns or with a Plasma Turret.