These are similar to Proto Lithian worlds, but they have a much higher metal content. They will have a large iron core with a thin, often martially molten, mantel rich in metallic content. They are geologically unstable, and may have molten metallic seas on the surface.
They are found around high mass or highly metallic stars, and are very rare.
Such worlds are too small and hot to retain an atmosphere, however continuous outgassing from the core will often result in an extremely thin atmosphere of exotic compounds. They may have a strong magnetic field that helps keep the atmosphere intact, but as soon as the world cools enough for the outgassing to cease, the atmosphere will not last more than a few million years.