The paper discusses the superconductivity of metallic boron in MgB$_2$. The authors, J. Kortus, I.I. Mazin, K.D. Belashchenko, V.P. Antropov, and L.L. Boyer, from the Naval Research Laboratory and Ames Laboratory, explore the electronic structure and electron-phonon coupling (EPC) in MgB$_2$. They find that boron forms honeycomb layers with magnesium as a space filler, resulting in a band structure where the Fermi level bands primarily derive from boron orbitals. The strong bonding and high phonon frequencies contribute to a significant electron-phonon coupling, estimated to be around 1. This, combined with high phonon frequencies between 300 and 700 cm$^{-1}$, explains the high critical temperature of MgB$_2$, which is consistent with recent experimental findings. The authors suggest that MgB$_2$ can be seen as an analog to the hypothetical superconducting metallic hydrogen, which has been a long-sought goal in the field of superconductivity. They also discuss the potential for optimizing the critical temperature through isovalent doping and lattice expansion.The paper discusses the superconductivity of metallic boron in MgB$_2$. The authors, J. Kortus, I.I. Mazin, K.D. Belashchenko, V.P. Antropov, and L.L. Boyer, from the Naval Research Laboratory and Ames Laboratory, explore the electronic structure and electron-phonon coupling (EPC) in MgB$_2$. They find that boron forms honeycomb layers with magnesium as a space filler, resulting in a band structure where the Fermi level bands primarily derive from boron orbitals. The strong bonding and high phonon frequencies contribute to a significant electron-phonon coupling, estimated to be around 1. This, combined with high phonon frequencies between 300 and 700 cm$^{-1}$, explains the high critical temperature of MgB$_2$, which is consistent with recent experimental findings. The authors suggest that MgB$_2$ can be seen as an analog to the hypothetical superconducting metallic hydrogen, which has been a long-sought goal in the field of superconductivity. They also discuss the potential for optimizing the critical temperature through isovalent doping and lattice expansion.