The yazatas Airyaman and Atar will melt the metal in the hills and mountains, and the molten metal will then flow across the earth like a river. All mankind—both the living and the resurrected dead—will be required to wade through that river, but for the righteous (ashavan) it will seem to be a river of warm milk, while the wicked will be burned. The river will then flow down to hell, where it will annihilate Angra Mainyu and the last vestiges of wickedness in the universe. In later Zoroastrian texts, it is written that the molten metal will purify the wicked.[3]
FWIW:
Wikipedia:Reference desk
https://en.wikipedia.org/wiki/Wikipedia:Reference_desk