A 17 percent slide in the stock of U.S. steelmakers over the past month illustrates, once again, that appearances in financial markets can be deceiving.

The selloff in companies tracked by Credit Suisse, from AK Steel to Nucor and U.S. Steel, actually represents a buying opportunity since the firms and their competitors are likely to benefit significantly from even the watered-down version of metals tariffs announced by President Trump on March 1, says Curt Woodworth, an analyst for the Zurich-based lender.