GTA V is many things and it has many features. It's a third/first-person action-adventure game, a shooter, an open-world driver, a crime-simulator, a great online experience. You can play golf, do yoga, go to a strip club, rob a bank, buy property, race against your friends, and steal cars. There is much mayhem to be caused, with a massive armory at your disposal, not to mention weaponized vehicles.
However despite all this, what GTA V isn't, is a modern military shooter. Until now.

Sure, GTA V has first-person view, and you can whip out your M4A1, but not matter how many wanted stars you have, GTA V won't suddenly turn into a Battlefield game. One particular modder set out to change that, and created a pretty nifty total conversion mod for GTA V's single player portion which turned the game into a militarized bullet storm. Battleground: Armored Packs adds various game-modes and mission types to GTA V. You can assist your dealer and his mates in fighting off hordes of cops, or call in a squad of PMC soldiers to help you out of a tight spot with rival mafia families.