Metallic Hydrogen exist in the inner core of Earth. Metallic hydrogen combines with oxygen brought down from the crust by way of convection currents to form superionic ice. This form of water has a melting point of 4700 Celsius, which means superionic ice can remain solid in the outer-core at (4400 Celsius.) As more metallic hydrogen is converted to superionic ice, the Earth expands - which drives plate tectonics of Earth's crust. Furthermore, superionic ice eventually rises to the surface through convection currents, increasing the amount of surface water.


https://www.quantamagazine.org/black-hot-superionic-ice-may-be-natures-most-common-form-of-water-20190508/?fbclid=IwAR3ZfY-kGUtDtZ_tbghR88tHBGvVxLG9mTK9zGwX8MFg8Rq2AeXPEmb5de8

https://www.nature.com/articles/268130a0

https://www.youtube.com/watch?v=pgm4z8vJVVk