The T-1000 is an advanced prototype android created by Skynet in the year 2029. It is perhaps the most effective infiltration machine that Skynet has developed and its very concept can be regarded as alien by the standards of the Resistance. Its entire structure is made up of a fluidic polymimetic alloy that can alter its shape and density. This allows the T-1000 to copy the appearance of any human being it comes into contact with. Because of this ability, the T-1000 does not suffer the cosmetic restrictions of the bulky T-800 infiltrators and can take the form of shorter, thinner, more frail humans that are more commonplace in the devastated future of the Terminator world. It can also form sharp metal blades and other close-quarter weaponry to terminate its targets, and its malleable liquid-metal body is completely immune to conventional firearms. Only electricity, magnetism and extreme temperatures can cause the T-1000 significant damage, making it very difficult to fight. They still cannot hide their scent from dogs, making Resistance sniffer dogs humanity's first line of defence against these virtually unstoppable killers. One consolation for the Resistance is that the T-1000 takes a great deal of time and material to produce, so Skynet has created very few of them.
Terminator 2: Judgment Day
In the Terminator 2 film, Skynet sends a T-1000 (portrayed by Robert Patrick) back in time to 1994 to assassinate the 10-year-old John Connor, who will grow up to become the leader of the Resistance in the war. Upon arrival, the T-1000 assumes the identity of a Los Angeles police officer, killing the officer and taking his gun and vehicle. Accessing the police database, the android finds the address of John's foster parents. John isn't home and so it takes to the streets and questions citizens regarding the boy's whereabouts, keeping a photo of John provided by his guardians.
John is located at a video arcade in a shopping mall and the T-1000 closes in, but its mission is interrupted by the arrival of a reprogrammed T-800 that the Resistance sent back to protect John. As the T-800 flees with its target, the T-1000 gives chase but loses them after crashing a truck in a canal. It then returns to John's home, hoping to reacquire him there, and kills the boy's foster parents and assumes his surrogate mother's identity. John later calls home but is confused by his "guardian's" pleasant manner. All the while, John's dog Max is barking outside, knowing that the T-1000 is an inhuman intruder. Using John's voice and referring to the dog as "Woofy", the T-800 fools the T-1000 into giving itself away and then hangs up. The T-1000 realises its error after killing the dog and checking its collar. Knowing that John isn't coming home, it anticipates that John will most likely try to reunite with his real mother, Sarah Connor.
The android drives to Pescadero Psychiatric Hospital to terminate Sarah and assume her identity, killing a guard on his way in and copying him. As it investigates, Sarah is already making her own escape attempt and is helped by her son John and his T-800 guardian. They make their escape and the T-1000 pursues, but is thrown off the group's hijacked car and loses them. After commandeering a police bike, it continues searching the city for its quarry. However, it is not until the Connors' assault on CyberDyne Systems that it manages to reacquire them.
The Connors flee in an armoured van and the T-1000 chases them down the highway in a helicopter. The T-800 manages to jump on to the low-flying chopper and bring it down, but as it crashes, so does the armoured van. The Connors and the T-800 take a small pickup truck that is abandoned by its driver, and the T-1000 continues its pursuit after hijacking a tanker full of liquid nitrogen. The chase continues all the way to a steel mill, where both vehicles crash and the tanker leaks its cargo. Upon contact with the nitrogen, the T-1000 begins to freeze, breaking off its limbs as it approaches its targets. It freezes completely and then the T-800 shoots it, shattering it to pieces.
The heat from the steel mill thaws out the T-1000's fragments, allowing it to reassemble itself. The transition from extreme cold to extreme heat damages the android's polymimetic matrix, causing it to destabilize. It continues its advance regardless and fights the T-800 one-to-one. The T-800 looses an arm and half its face in the struggle and is impaled with a steel rod. This does not destroy the cyborg, however, as its back-up power cell kicks in shortly after its primary battery goes down. Just as Sarah has used the last of her ammo to no avail and she and John are cornered over a pool of molten steel, the T-800 emerges from behind a large gear and blasts the T-1000 with a grenade launcher. The explosion warps the T-1000's body like a pretzel and it staggers back and off the platform, falling into the white-hot steel below. The android thrashes about as though in pain, as its structure is broken down by the immense heat and it is completely melted away.
In the rewritten timeline of Terminator: Genisys, a T-1000 (portrayed by Byung-hun Lee) was sent back in time by Skynet to 1973 on a mission to kill Sarah Connor while she was still a child. While it succeeded in killing Sarah's parents, its mission was interrupted by the arrival of the Guardian, a re-programmed T-800 sent back by an unknown party to protect Sarah. The Guardian rescued Sarah and fled with her, but the T-1000 would eventually track her down again.
In 1984, the T-1000 was in Los Angeles awaiting the arrival of Kyle Reese, a Resistance soldier sent back to protect Sarah. Disguised as a police officer, the android almost succeeded in terminating Kyle but was stopped by Sarah and the Guardian. Sarah and Kyle fled together in an armoured truck, but the T-1000 was able to track them by shedding a small fragment of itself and planting it on the truck. It followed them to an abandoned warehouse and used another sliver of its own polymimetic alloy to reactivate an inert T-800 that the Guardian had incapacitated earlier. It also immobilized the Guardian by forming a spear and pinning the older android to a wall. As the reactivated T-800 went after Kyle, the T-1000 confronted Sarah.
After a brief confrontation, Sarah lead the T-1000, who impersonated Kyle, into a large room with barrels of highly corrosive acid under a grate on the ceiling. It tried to confuse Sarah with the real Kyle, but she guessed (correctly) by shooting one of the Kyles in the foot. She then shot the acid containers on the ceiling, which corroded the Terminator to almost the point of immobility; this did not completely stop it, as enough polyalloy remained to still form a semi-coherent form that it used to slash at Sarah. It only got a couple of strikes in before Pops, who had since freed himself from the T-1000's spike, finished it off by holding it under the acid shower until it corroded into nothing.
- Shapeshifting - The T-1000 can assume the form and voice of any human being and can form solid metal objects such as knives and stabbing weapons. It can also spread its mass out so thin that it can blend into the surrounding environment.
- Immunity - The T-1000 cannot be harmed by conventional firearms. It is only vulnerable to electricity, magnetism and heat.
- Regeneration - Any wounds the T-1000 sustains can be regenerated swiftly. If any of its mass is separated, it will revert to liquid and will attempt to reintegrate with the rest of it.
- Shedding - The T-1000 can separate fragments of itself at will which it can use in various ways. For example, it can form projectile weapons with these fragments, such as javelins. It can also use any severed parts of itself as tracking devices, planting any shed portions of polyalloy onto a target vehicle to trace its movements. The T-1000 can also use polyalloy fragments to provide field repairs to damaged Terminator units, as demonstrated in Genisys when it sheds a drop to reactivate an inactive T-800.
- Electromagnetism - Strong electrical currents can short out a T-1000's sensory input and magnetic fields can disrupt its ability to hold its shape and even immobilise it.
- Extreme temperatures - Extreme cold can cause the T-1000 to freeze solid and extreme heat can disrupt its shapeshifting ability, causing it to inadvertently blend or fuse with its surroundings. Prolonged contact with any heat source in excess of 1500 degrees Celsius will destroy it.
- Acid - Caustic fluids such as sulphuric acid will dissolve polyalloy.
- The T-1000 can only form objects of equivalent size and mass, so it cannot transform into things such as a houseplant or a pack of cigarettes. Also, it is unable to form guns or any complex devices with moving parts or chemicals.
- Since it has no solid components or circuitry, the T-1000 cannot be reprogrammed (assuming that the Resistance could ever capture one). Only Skynet would have the technology for such a task.
- If severely damaged by extreme heat/cold, the T-1000's shapeshifting ability will become unstable. This can result in slower regeneration, partial merging with the surrounding environment and inability to maintain a single form.
- Skynet's time-displacement equipment will only transport living matter or objects sheathed in living matter (eg. Terminators with all their flesh intact), but the T-1000 is made entirely of metal which, although liquid, is still non-living. It has not been explained in film how Skynet could send a T-1000 back without any flesh covering.