The grunts charge at their enemies and detonate their methane bombs, causing massive splash damage. These Grunts have large, cylindrical methane tanks on their backs which hold far more of the gas than other Grunt's tanks. In Halo Wars, Suicide Grunts are a special forces unit, starting with a plasma pistol, being only the leader-specific unit of the Arbiter. These Grunts are generally referred to as 'Kamikaze Grunts' or 'Suicide Grunts'. In Halo 3 and onward, Grunts have a tendency to arm two Plasma Grenades and rush to the player, causing an explosion as a result of their Elite or Brute leader being killed in a brutal way (ie, being stuck with a plasma grenade, shot in the head or blown up by a Needler).

They have been known to 'spam' Plasma Grenades on the Legendary difficulty, which means that in a group of 10 Grunts, as many as eight of them will throw Plasma Grenades, one after the other, in an attempt to easily dispatch their foes. With the Catch skull enabled, Grunt Heavies have been observed throwing upwards of six plasma grenades. Certain commanders also outfit their troops with specialized weaponry (or none at all in the case of Yapyap's Cannon Fodder), such as Decimus's Bloodfuel rifle.ДЄll Grunts are equipped with, and often use, Plasma Grenades, although higher-ranking Grunts such as Ultra Grunts, Special Operations Grunts and Grunt Majors throw grenades in combat more often. While plasma pistols and needlers are still the most common, the Disruptor and Mangler can also be found in the hands of higher ranked grunts. Grunts in the employment of the Banished are observed with a wider range of weaponry. If a Grunt is in a Phantom that is shot down, and somehow manages to survive, it will sometimes be wielding a Spiker. On The Storm and The Ark, a Grunt can be seen with a Brute Spiker. Grunt Heavies can carry folded Plasma cannons. Special Operations grunts and Grunt Heavies are occasionally seen bearing Fuel Rod Guns.

Grunts are almost never seen equipped with two-handed weapons like Covenant Carbines, Brute Shots, Type-50 particle beam rifle, etc. Their combined fire, even with weaker plasma pistols, can quickly erode an enemy's shields. Grunts are often armed with the ubiquitous Plasma Pistol, although they are often seen wielding Needlers and Fuel Rod Guns. They also have a tendency to over charge their plasma pistols, which drains the battery significantly, but can completely drain an enemies shields, or cause vehicles to temporarily stop working. Occasionally, when driven into a corner, Grunts will commit suicide be detonating two plasma grenades in close proximity to their target. Higher-ranking Grunts may not run away, but instead, keep fighting after the leader has fallen.

Grunts can be tenacious fighters as long as they have someone leading them. Grunts working in cooperation with Jackals are very good at seizing the initiative to flank unsuspecting enemies as well. There are times they take advantage of their small size they can easily hide and ambush or surprise their enemies with an overcharged plasma bolt or grenade. Small groups of Grunts are generally used to slow enemy movements or deal minor damage to weaken enemy forces, and force them to waste ammunition and time. Typically, Grunts fight by having the Minor Grunts combine their firepower to soften and lower the enemy's shields, so that their more dangerous allies can finish off enemy units more easily. Most of the time, when their leader is dead, Grunts will run away, even the higher-ranking ones. Grunts usually fight in groups consisting of mostly low ranked Grunts, one or two higher ranked Grunts, and an Elite or Brute leader. However, in groups they are destructive and violent.

Halo 1 grunt