Investors are bracing for the weekend attacks on Iran to ripple through markets. Front and center is the oil market, and the looming threat to energy flows.

The Strait of Hormuz is among the world’s most important global shipping lanes, with 13 million barrels of crude oil per day flowing through the waterway in 2025, about 20% to 30% of the world’s supply. Reports on Saturday indicated that Iran was moving to close the strait. That represents a worst-case scenario for markets that could send crude prices sharply higher when trading resumes on Sunday evening.

Here’s what to watch as investors react to the strikes on Iran.

‘Worst fears’ for oil

“Oil markets might have to face their worst fears on…