Metallic gas – medium for gas lasers
Metallic gas is actually nothing other than a laser medium. Neon gas, for example, is a metallic gas, just as helium and hydrogen. These gases are found in the highest concentration on Jupiter.
Hard to believe, but due to the atmospheric conditions there, they change directly from a gas state to a liquid state. And that means: On Jupiter, it is practically raining metallic gas.
Down here on earth, metallic gas is used in helium neon lasers, for example. These laser types are especially used for holography.
Although they have now been mostly replaced by other devices, they also used to be integrated in bar code scanner units for tills and in laser printers. One form of metallic gas is metallic hydrogen. That is actually only the specification for hydrogen under high pressure.