Registeel is a large Legendary Steel-type Pokémon. Most of Registeel's body is spherical and gray while the middle of its face has the appearance of being exposed as it shows black "skin" and is surrounded by raised metal. Registeel's lower half is disc-like in shape and has two cylindrical legs without toes. Its face consists of seven red dots in a hexagonal formation and it has black arms with three fingers each that are connected to its upper half by gray hemispheres. The backs of its hands have three red triangles pointing away from the fingers.
While Registeel has been classified as a Steel-type Pokémon, its body is hollow and made of a material that is harder than any known metal. However, this material stretches and shrinks despite its hardness. Because of this, it is unknown what Registeel can eat. Registeel's body was tempered by pressure underground over thousands of years, as a result, it cannot be scratched. It was sealed away in ruins by people during ancient times.
Its body is harder than any other kind of metal. The body metal is composed of a mysterious substance. Not only is it hard, it shrinks and stretches flexibly.