The metallic state exists in HMTSF-TCNQ under pressure (in excess of 2.5 kbar) down to the lowest measured temperatures (~ 20 mK). It is characterized by a large, anisotropic magnetoresistance, a high mobility (~ 40000 cm2/V s), Landau-Peierls diamagnetism, Shubnikov-De Haas oscillations, and a peculiar band structure. It requires that the tunneling matrix element between chains, t⊥, be bigger than the inverse collision time along a chain, [MATH]. Then the tunneling time between chains, τ⊥, becomes shorter than τ≥. In contrast, in the true one-dimensional state, τ⊥ > τ≥ and is given by τ-1⊥ = [MATH], and can be measured directly by NMR. The anisotropic three dimensional, and the true one dimensional, metallic states are characterized and compared. The collision rate τ-1≥ is mainly due to second-order scattering by librons, though several other possible mechanisms have been proposed. While the true one-dimensional state undergoes a Peierls transition, the anisotropic three-dimensional state is frequently superconducting in inorganic compounds, but superconductivity has not yet been observed in the organic metallic state