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An answer combines infrared reflectivity showing a Drude response, dc electrical transport, and structure determination above $\\sim 4\\,\\mathrm{Mbar}$.","problem_ref":null,"references":"","settled_by":"Reproducible dc transport with metallic temperature dependence plus diffraction or Raman identification of the phase, at a stated calibrated pressure.","status_note":"Synchrotron infrared data (2020) showed a first-order gap collapse near 4.25 Mbar at about 80 K; the 2017 reflectivity claim at about 4.95 Mbar and dc confirmation remain disputed.","title":"At what pressure does solid hydrogen become a 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