Lots of action, lots of action, lots of destruction. I guess there was some kind of plot and I think there were characters, although I did not care about either. Great effects, lousy movie.
Leonard Maltin/Plot synopsis:
When Tony Stark and Bruce Banner try to jump-start a dormant peacekeeping program called Ultron, things go horribly wrong and it's up to Earth's Mightiest Heroes to stop the villainous Ultron from enacting his terrible plans.