"Molten iron" refers to the metal iron that has been heated to a very high temperature, causing it to melt and become liquid-like instead of solid. Full definition
It might be produced from a partially molten iron core in the planet's interior. (solarviews.com)
Heat from Earth's inner core, which is as hot as the surface of the sun, churns an outer core of molten iron and nickel, generating a magnetic field that deflects lethal cosmic and solar radiation away from the planet. (discovermagazine.com)
Siderophiles, elements including gold, platinum and palladium, dissolve in molten iron. (newscientist.com)