It's tariff time.

The Trump administration announced a 25% tariff on imported steel and a 10% tariff on imported aluminum during a press conference Thursday

The president said that he was protecting America's national security by regulating the inflow of foreign metals. Trump also played up the nationalist angle of his plan, saying that the move would help struggling U.S. steel plants. The duties are set to take effect in 15 days.

It's trade war time.

— Brian Sozzi (@BrianSozzi) March 8, 2018

Oddly enough, steel stocks tanked by the close.

Steel Dynamics Inc. (STLD) fell 2.8%, while AK Steel Holding Corp. (AKS) dropped 3.96%. Olympic Steel Inc. (ZEUS) declined 3.6% and U.S. Steel Corp. (X) fell 2.9%. The SPDR S&P Metals and Mining ETF (XME) , which has more than 50% allocation to steel companies and more than 12% allocation to aluminum companies, was down 2.04%.