From Combine OverWiki, the English Half-Life Wikia
The Grunts are known as the soldier class or creations of the humanoid Vortigaunt race of Xen, and the primary combatants of the Xenian Army. Tough, strong, and extremely hostile, Alien Grunts are armed with a biological weapon called the Hivehand, which contains Hornets; insect-like flying creatures that seek out living targets and attack them. Hornets (also known to some as Thornets) respawn as an apparently infinite supply of ammunition. The Grunt will also punch anything that gets too close with its thick bulky arms that end in blunt pincers. Alien Grunts share many features with their Vortigaunt counterparts: multiple red eyes, backwards-jointed legs, hoofed feet and a short arm extending from their mid-torso which is used for feeding. However, they do not seem to share the race's myriad energy-based powers, hence the need for the hivehand weapon. At one point in the game, a group of alien grunts appear to be commandeering, or at least have set up, an alien energy cannon, implying the necessary requirement of external weaponry. Grunts are equipped with metallic armour around the groin and shoulders, as well as metal helmets and shoes.
The Alien Grunts can be found being transported through a factory on Xen, stored in pod-shaped containers. The implication is that the Alien Grunts are manufactured beings, an idea that is substantiated by their shining, metallic armour that appears surgically attached. They are carried into combat zones through the use of Xen manta ships.
