Metallic warriors wield mass destruction at RoboGames (audio slideshow)

Team of builders and engineers are repairing wounds, testing hydraulics, charging batteries, and sharpening weapons in preparation for the next round of matches following Friday's fierce battles during the opening day of RoboGames, the world's largest open robot competition.

The three-day competition, which opened Friday at the San Mateo Fairgrounds, features more than 50 robot games and challenges, sporting events, and contests, from sports like soccer and sumo wrestling to climbing, shooting galleries, and weightlifting, but the big draw is the awesome power of the combat robots.

In weight classes up to 340 lbs., these monstrous machines are fast and deadly. Covered in armor and outfitted with frightening weapons that spin, hack, flip, and saw, teams come from around the world to compete in these events in which hundreds of hours of work and thousands of dollars in parts can be destroyed in seconds.