Met

Met, alternatively known as, Mettaur, is a hazard that appears on Skull Fortress in Super Smash Flash 2.

Character description
These robots have appeared in almost all incarnations of the  series, with the exception of Mega Man Legends (although the character Bon Bonne resembles a Met and Shekutens behavior is likely an homage to Mets). Their full name has been rendered in English as Metall or Mettool in earlier appearances. They didn't have a consistent localization in English until 2004 when the name Mettaur was used in all western Mega Man games since. They are also unofficially called Hard Hats in some strategy guides. Mets wear an indestructible hard hat that makes them invincible while hiding under it, although a few games allow the player to bypass this. For example, they can be flipped with Oil Slider in Mega Man Powered Up and with guard breaking attacks in Mega Man X8.

In Super Smash Flash 2
A small recurring robot enemy that wears an "indestructible" hard helmet, it appears in almost every Mega Man sub-series to date. Though they are found most common as enemies, there are also bigger variation that work as mini-bosses or even bosses.