Once told they'd save the universe during a time-traveling adventure, 2 would-be rockers from San Dimas, California find themselves as middle-aged dads still trying to crank out a hit song and fulfill their destiny.
 
I'm not going to waste your time.  You should only watch this movie if you're a fan of the franchise.  It's not as good as the first two, but it's still fun and has a couple of scenes I will be quoting for the rest of my life.  
 
FUN FACT:  During filming in a neighborhood in Louisiana, the cast and crew were often greeted by local residents. One day, Keanu Reeves noticed a sign on a lawn that read "You're breathtaking". He stopped, got out of the car, went to the sign and autographed it. After finding out who the sign belonged to, he went to the family and posed for a photo with them.