In the 1991 film "Terminator 2: Judgment Day", the liquid metal terminator's model number is T-1000.
The T-1000 is an advanced prototype sent from the future to eliminate John Connor before he can become the leader of the human resistance. Unlike the reprogrammed T-800 protecting John, the T-1000 is made from a fictional mimetic polyalloy: a liquid-like metal that can flow, reshape itself and imitate people or objects.
Robert Patrick portrays the T-1000, whose lean appearance and calm movements deliberately contrast with Arnold Schwarzenegger's bulky machine. The terminator commonly copies the appearance of a Los Angeles police officer, allowing it to move through public spaces while searching for John. Its abilities let it form blades and pass through bars, but it cannot convincingly reproduce complex machinery or weapons with moving parts.
A frequent mix-up is calling the liquid-metal character a T-800, which is the earlier, solid endoskeleton model played by Schwarzenegger. T-X is a different advanced terminator introduced in Terminator 3, while T-1001 is not the model identified in Judgment Day.