Mettaur (メットール,Mettōru?, Metall in Japan) are common enemies in the Mega Man series.
Although they were originally created as industrial robots, Dr. Wily stole and reprogrammed them as a battle type robot to fight against Mega Man. They are also the main mascot of the Mega Man series, and although they appear in various versions, they usually act like Goombas, walking towards Mega Man, and shoots a 3-way buster shots when Mega Man is near them for few seconds. They're easily defeated with a single shot, but as they're equipped with a helmet, they can protect themselves from Mega Man's shots by hiding underneath the helmet.
In Super Smash Bros. 3DS/Wii U
Mettaurs are set to appear in Super Smash Bros. for Nintendo 3DS as common enemies in Smash Run. They only stay in one place as they cannot move around, but shoots a 3-way buster shots at players, and hides underneath the helmet for protection, which is similar to the attack pattern of the Octorok.
This enemy comes to Smash Bros. from the Mega Man series, bringing its distinct yellow helmet along with it. Usually hiding under its helmet, every so often a Mettaur will show its face to fire off a few shots. You can't hurt them when they hunker down, but you can grab them...