So I need some clarification because this is relating to a novel I'm writing. What are the differences between Metallic Hydrogen and Ice XiX (19) I'm pretty science illiterate but are these just the same thing going by different names? I really need to know if this is a crystal taking on fluid properties or a liquid taking on solid like Metallic properties do to extreme pressures. Spoiler: Why I want to know I posted a question like 3 or 4 yrs ago about Metallic water I remembered from a documentary I watched in 2007 and they finally produced it and I think it's very interesting
Metallic Hydrogen is ultra high pressure and temperature hydrogen though to be found in the center of gas giants and stars. Ice 19 is ultra high pressure and low temperature ice that is made in a lab. Other than being extremely rare and existing and very high pressure, they have nothing in common.
AIUI the various exotic "ice" crystals produced at extremes of pressure & temperature are still water (H2O), whereas "metallic hydrogen" lacks the Oxygen component, making just H2 (or perhaps some other H-only molecule structure).