Looking to bourses, the U.K.'s FTSE 100 closed down 1.47 percent, while France's CAC 40 tumbled 2.39 percent and Germany's DAX slid 2.27 percent.
On Thursday, Trump said the U.S. would impose a 25 percent tariff on steel imports and 10 percent on aluminum, which could end up hurting companies both inside and outside the U.S. Some analysts argued that U.S. businesses would still have to import such materials while steel and aluminum production develops, potentially meaning higher costs for consumers.
The European Commission has since responded, saying it won't sit idly and will take the decision to the World Trade Organization (WTO). Trump's decision could potentially lead other countries to raise tariffs on products that U.S. consumers buy.
The negative sentiment was seen across global markets Friday, with Asia closing deep in the red and stocks on Wall Street sliding, with the Dow off over 250 points at Europe's market close. Europe's basic resources fell 3 percent, making it the worst performing sector, as miners slipped on the news.
At the same time, recent comments from newly-appointed Fed Chairman Jerome Powell put markets on edge, after he said there are no signs that the U.S. economy is overheating. Investors have become more certain that the Fed will increase rates at a faster pace in 2018.