LMG Technicians are Monarch Security troopers clad in heavy armor and wield Light Machine Guns.
LMG Technicians are among the most dangerous standard Monarch soldiers in the game. For one, their machine guns are a powerful, rapid source of damage, which can be distributed across shockingly long ranges. They are able to withstand more punishment than most other enemies, save for the Juggernaut, and are capable of moving surprisingly quickly given their heavy armor. The backpack they wear grants an infinite supply of ammo, so they will have plenty of opportunities to flush Jack into cover. And above all, in later parts of the game, they will be equipped with a Chronon Dampener, which will make them even more dangerous at closer ranges because Jack will not be able to use his time powers.
However, as fearsome as these enemies are, they are usually slow. Flanking them is a rewarding tactic, but it is best to fight them from a distance using the Carbine Rifle or other long-range weapon, as it is generally far too risky to face an LMG Technician up close, since they can rip you to shreds.