If
hydrogen is sufficiently compressed then it will undergo a
phase change and
Metallic Hydrogen will result. Metallic hydrogen is an example of
degenerate matter. It consists of a lattice of
atomic nuclei (namely
protons) with a spacing that is significantly smaller than a
Bohr radius, indeed more comparable with an electron wavelength. The electrons are unbound and behave like the
conduction electrons in a
metal.
Popular models of the planet Jupiter hold that its core is rich in metallic hydrogen.