In an attempt to make their country safer, the U.S. military obtained the technology and patents to an experimental computer program from the destroyed Cyberdyne Systems Corporation, using it to network its various combat systems to link up globally and build robotic troops to replace its human components, this program was called Skynet.

However, in July of 2004, the U.S. military computers are besieged by a computer virus that seems to have spread throughout the nation, affecting anything electronic. In an attempt to combat this threat, the military brings Skynet online to destroy the virus, unaware that the attack is actually a trick and soon after being brought online, Skynet becomes sentient and launches an attack on its biggest threat...mankind. One hour after becoming sentient, it launches a nuclear barrage across the globe, striking key cities, destroying military assets and bringing mankind to the brink of destruction. This day is known as Judgement Day.

Twelve years later, the survivors of Judgement Day are in desperate need of salvation as Skynet uses machines to hunt down and wipe out mankind. However there is a hope, a man by the name of John Connor who has fought Skynet in the past as it has sent machines known as Terminators into the past, once before he was born, when he was a teenager and right before Judgement Day. Knowing how to combat these machines, Connor fights alongside a branch of Resistance fighters in the wasteland formerly known as Los Angeles, trying to stop Skynet while protecting his squad as well as his wife from being wiped out.

While the game does share the name of the 2009 movie, it does not follow the plot of the movie, instead it is set two years before in 2016 and bridges the gap between Terminator 3 and Terminator Salvation. The player takes control of Connor as they transverse through apocalyptic settings, fighting off terrifying machines that range from HK's (Hunter Killers), T-1 tanks, spider machines, motor terminators and the dreaded T-600, attempting to rescue captured soldiers while encountering other characters to help them in their quest.

The gameplay is mostly a third-person shooter, similar in style to Gears of War, where the player uses weapons such as small caliber firearms, larger assault weapons, grenades and rocket launchers to fight off various ground and air enemies while using various obstacles for cover from enemy fire with some on-rail vehicle shooting stages scattered in between. Players can only carry two weapons at a time, but can swap them out for other weapons (however, they can not pick up weapons from fallen Terminators) and can carry one type of throwing weapons (grenade, pipe bomb, etc.).

The story is told through pre-rendered CGI cutscenes and does not feature any online multiplayer functions, but does have an offline two-player split-screen co-op mode that allows two friends to fight side by side in the story mode. Additionally, actors Common and Moon Bloodgood lend their voices to the games to reprise their roles, but does not feature the voice of Christian Bale as John Connor, instead Gideon Emery voices Connor. Rose McGowan also lends her voice to the game as well as Kelly Hu.