When the Lord comes at the end of time he comes in power. That power will be so great that none can resist his right to rule. It is in this context that Malachai asks, “who shall stand when he appeareth?” The “standing” mean s to stand against, or to resist.
A refiner’s fire is the heat that is applied to metals to melt out the impurities. The fuller’s soap cleans the dirt from leather goods. Both of these are cleansing and purifying metaphors. The arrival of the Lord in the last days will not simply be one of military victory, but one of purification of the world.