Matt is a young dude who is obsessed with sex and lives in an '80s horror film. Yep, this guy is gonna catch some death.
Matt calls Ginger to engage in a little phone foreplay but accidentally gets Sarah on the phone instead. Embarrassed but undeterred, he shows up at their apartment later and engages in more than foreplay with Ginger. True to horror-movie rules, after they have sex, the Terminator arrives and kills both of them, mistaking Ginger for Sarah Connor.
In the end, Matt's main purpose is to serve as a foil for Reese. Both men love their respective women, but Matt's love is more immature. As far as we know, it is based entirely on sexual attraction, unlike Reese's more mature love. This is partly due to the very different worlds the two men come from. Matt's world is the light-hearted, often shallow world of present-day America, whereas Reese's world is a dystopian future that makes Hunger Games look a nature walk.
To give credit where it is due, Matt does attempt to protect Ginger from the invader, and he busts the Terminator in the chops with a lamp. If a 260-pound, 6-foot-tall Austrian bodybuilder snuck into our house, we'd probably just have snagglepussed it out of there.