Metalkind

The "Metalkind" were a race of boron-based lifeforms.

History
The Metalkind went to war with a Fleshkind race that lived on the twin planet of their homeworld after they mined ore (In actuality, the Metalkind's children) from the Metalkind planet. The war raged on for hundreds of years before the 21st century.

When the Fleshkind lost a living weapon that could destroy the Metalkind, on Earth, a Metalkind came to the planet in search of it. The Metalkind was damaged when the weapon unleashed her energies against it. The creator of the weapon, Myers, used the Metalkind to summon his race to Earth, intending for her creation to destroy them all. Myers' plan was foiled by Sarah Jane Smith and her allies. The Metalkind then freed itself and took Myers with it back to its homeworld. (SJA: Sky)

Behind the scenes

 * The biology of these creatures somewhat resembles that of Cybermen of Mondas. Both the Metalkind and the Cybermen are organic, metal-based humanoids. But while the Metalkind are natural metal-based lifeforms, Cybermen are normally carbon-based lifeforms with cybernetic alterations.