Cyborg 2087 (1966)

Starring Michael Rennie, Karen Steele, Wendell Corey, Warren Stevens, Eduard Franz
Directed by Franklin Adreon
(actor & director credits courtesy IMDB.com)

A cyborg is sent back in time to prevent a kindly scientist from revealing his method of radio-telepathy to the military, as in his time it has transformed the government into an oppressive regime.

Almost 20 years prior to The Terminator, we have Rennie as a cyborg with a not too dissimilar mission, although his aims are far more benevolent and he doesn't carry a lethal weapon.  Give screenwriter Arthur C. Pierce credit for coming up with the premise, and I wouldn't put his screenplay up against that later film's, although this one's a lot more in my wheelhouse.  As a low-budget offering from United Pictures, it may not be a great film, but I enjoyed it immensely, and there's a cast full of genre veterans, including The Day The Earth Stood Still's Rennie, Steele, who played Eve McHuron in Star Trek's famous "Mudd's Women" episode, Forbidden Planet's Warren Stevens, and Eduard Franz from The Four Skulls Of Jonathan Drake.  The special effects are sparse and unimpressive, but Rennie fits the bill as the emotionless future man who may have feelings after all.  I loved the fact that the film climaxes with a knock-down drag out fight between two cyborgs, in the style of a serial fistfight, which director Adreon had some experience with.  There were also a number of scenes that made me laugh, from the crazy dancing of Stevens' daughter and her friends, to an evil counterpart of Rennie's getting Steele to scream not by torturing her but by hanging her in midair by her knuckles and pushing her so she swings.  Composer Paul Dunlap also comes up with slightly goofy chase music for the cyborgs on Rennie's trail which adds to the fun.