European stocks on Friday logged their lowest close in three months, flattened partially by a decline in shares of UBS following the Swiss bank's earnings. The Stoxx Europe 600 SXXP, -1.04% dropped 1% to end at 378.34, the weakest close since April 21, FactSet data showed, and only the oil-and-gas sector SXEP, +0.24% finished higher.

Asian shares generally started Monday with slight declines as investors took profits on the last day of a largely positive month for stocks in the region that benefited from robust earnings and higher commodity prices. Traders want to hold cash as the possibility of tax and infrastructure overhauls in the U.S. fades, said Hao Hong, head of research at BOCOM International in Hong Kong.

The U.S. stock market has been on such a parabolic march higher that Wall Street investors may have forgotten what a typical, sharp downturn feels like. Indeed, much has been made about the lack of volatility. The CBOE Volatility Index VIX, +1.78% otherwise known as the "fear gauge," had been flirting with its lowest close on record, implying that market expectations for a sharp, sudden fall are near rock bottom, as the Dow Jones Industrial Average DJIA, +0.15% S&P 500 index SPX, -0.13% and the Nasdaq Composite Index COMP, -0.12% scale new heights.