The periodic table of the elements arranges elements horizontally according to atomic number. Vertically, they are arranged according to similarities in structure and activity. Column I contains the alkali metals, which are lithium, sodium, potassium, rubidium, cesium, and francium. They all have one free electron in their outer shell, which makes them very reactive. They are softer than other metals but, like all metals, they are good conductors of heat and electricity. One is missing, though. The element at the top of the first column is hydrogen, which is not normally considered when talking about metals.
We all know hydrogen as a very light gas. It was theorized quite some time ago that at very high pressure hydrogen would show metallic properties, especially the ability to conduct electricity. In 1996, Lawrence Livermore National Laboratory succeeded in creating in creating metallic hydrogen. It required a pressure of more than a million atmospheres and it only existed for a microsecond. They were also subjecting the hydrogen to very high temperature and because of that, did not expect to produce metallic hydrogen. It was previously thought that very low temperatures would be required.
It is possible that metallic hydrogen exists inside Jupiter and Saturn. If it is there, there is at present no conceivable use for it. Theoretically, metallic hydrogen might be a superconductor at room temperature, but that has no practical value, either, as the cost of creating the tremendous pressure required is much greater than the cost of producing the very low temperatures required for known superconductors.