Shares of steel and aluminum companies like Cleveland-Cliffs Inc. (CLF), Steel Dynamics Inc. (STLD), United States Steel Corp. (X), and others surged on Wednesday as U.S. President Donald Trump’s proposed tariffs took effect.

Cleveland-Cliffs led shares of steel and aluminum companies in reaction to tariffs on imports of the metals implemented by the Trump administration.

The CEOs, which include Cleveland-Cliffs Inc.’s Lourenco Goncalves, Nucor Corp.’s Leon Topalian, and United States Steel Corp.’s David Burritt, argued that avoiding exemptions was a matter of national security.

Trump's action to bulk up protections for American steel and aluminum producers restores effective global tariffs of 25% on all imports of the metals.

Global markets have been gripped by a sense of risk aversion ever since U.S. President Donald Trump triggered a tit-for-tat tariff war between the U.S. and its trade partners, which analysts have said could stoke inflationary pressures and trigger an economic slowdown.