Over an apocalyptic battlefield dominated by robotic war machines, some like tanks, others are hovercrafts, a title card tells us that in the future, humans will wage a long war against an enemy known as the Machines. The "final battle" however, will not be fought in this future world, but in the past, specifically our present.
The year switches to 1984. Lighting emanates from above a garbage truck, knocking out power. The driver sees an object ahead of him and flees as the electrical surge dissipates. The object is a man (Arnold Schwarzenegger), naked and heavily muscular, and he stands up and starts walking toward the city where he is spotted by three young punks. The man orders the men to give him their clothes, and the punks produce knives in response. The giant swats two punks aside, the third stabs him, but the giant tears open the punk's body and kills him, taking his clothes.
In a downtown alley, a homeless man sees a bright light just above the ground. A scarred, naked man, muscular but much smaller in size than the other man who arrived in a similar fashion, is forced through the portal and lands in the alley, in obvious pain. The naked man takes the homeless man's clothes, just as a police car pulls up and two cops yell at him to freeze. The man is able to hide and attacks one of the cops, taking his pistol. The cop becomes puzzled by the man's question of the date and year. When the cop's partner arrives, the man runs into a department store. He steals several items, including a pair of Nike sneakers and a long coat and escapes the store. In another alley outside, he steals a shotgun from an unoccupied squad car. Finding a phone book nearby, he looks up the name "Sarah Connor.".