When the Messiah comes at the end of time, he will come in irresistible power. None will be able to resist his right to rule. This is the context for Malachi’s query: “Who shall stand when he appeareth?” “Standing” means “stand against” or “resist.”
Vocabulary: A refiner’s fire is the heat applied to metals to burn out impurities. Fuller’s soap cleans dirt from leather. Both metaphors are of cleansing and purifying. The Messiah’s arrival will not only be military victory but purification from worldly corruption.