From the Super Mario Wiki
Goombeetles (called Metallic Goombas in the Prima strategy guide) are a type of Goomba only found in Super Mario Galaxy and its sequel Super Mario Galaxy 2. They are basically regular Goombas that wear protective helmets, which prevent them from being stomped on. They seem to be the Goomba equivalent of Buzzy Beetles, due to the similar name and the helmet they wear which acts like a Buzzy Beetle's shell, as they are used to protect themselves from attacks.
Super Mario Galaxy
Goombeetles first appear in Super Mario Galaxy. They are mostly found in Bowser's and Bowser Jr.'s galaxies. They are also found in the Buoy Base Galaxy and the Dreadnought Galaxy. They attack by charging at Mario, just like regular Goombas. However, unlike regular Goombas, they cannot be defeated by being jumped on. To defeat them, Mario must flip them with a Spin and then jump on them. Each one defeated releases a coin. If they are, however, defeated with a Bullet Bill, they will release three Star Bits.
Super Mario Galaxy 2
The Goombeetles reappear in Super Mario Galaxy 2. They act and appear the same way as they did in the previous game. They appear in Bowser Jr.'s Fiery Flotilla, Beat Block Galaxy and Chompworks Galaxy. They can be defeated by the Co-Star Luma or instantly defeated by a Chomp, which like the previous game causes them to release three Star Bits.
Goombeetles differ from Goombas in other ways than the fact that they wear protective helmets on top of their heads. More differences include their eyes which are not white like most other Goombas' eyes but are instead yellow-colored and just visible in the darkness of the helmet.
Names in other languages
|From メット metto "helmet" and クリボー kuribō "Goomba".
||From Goomba and "elmetto", helmet