Jesus compared His return to the time that God destroyed the cities of Sodom and Gomorrah,

“Likewise as it was also in the days of Lot: They ate, they drank, they bought, they sold, they planted, they built; but on the day that Lot went out of Sodom it rained fire and brimstone from heaven and destroyed them all. Even so will it be in the day when the Son of Man is revealed (Luke 17:28–30).

The people of Sodom thought everything was wonderful and that they had no reason to fear the end of their wonderful lives, but Genesis 19 shows what happened, and Jesus summarized it, saying that fire and brimstone fell from heaven and destroyed all the people.

When Jesus returns, people will be eating, drinking, buying, selling, planting, building, and just enjoying life, but suddenly He will appear from heaven, and those who do not belong to Him shall also experience fire and brimstone.