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.

Oddly enough, steel stocks tanked by the close.

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