In Terminator 2: Judgment Day, the liquid-metal model sent back to kill John Connor is the T-1000.
The T-1000 is a prototype Terminator made from mimetic polyalloy, a fictional material that lets it reshape its body and imitate people it touches. Robert Patrick plays the machine, whose quiet appearance contrasts with its extraordinary physical abilities.
The T-1000 is sent to 1995 to assassinate the young John Connor. A reprogrammed T-800 is sent to protect him, creating the central machine-versus-machine conflict of the film.
The T-1000 is not the same model as Schwarzenegger’s T-800. The T-800 has a solid metal endoskeleton covered by living tissue, while the T-1000’s entire body can flow and reform. James Cameron directed the 1991 sequel.