President Trump announced sweeping tariffs on foreign steel and aluminum on Monday, re-upping a policy from his first term that pleased domestic metal makers but hurt other American industries and ignited trade wars on multiple fronts.

The president signed two official proclamations that would impose a 25 percent tariff on steel and aluminum from all countries. Mr. Trump, speaking from the Oval Office on Monday evening, called the moves “a big deal.”

“It’s time for our great industries to come back to America,” the president said.

A White House official who was not authorized to speak publicly told reporters on Monday that the move was evidence of Mr. Trump’s commitment to use tariffs to put the United States on equal footing with other nations. In contrast with Mr. Trump’s first term, the official said, no exclusions to the tariffs for American companies that rely on foreign steel and aluminum will be allowed.

The measures were welcomed by domestic steelmakers, who have been lobbying the Trump administration for protection against cheap foreign metals.

But the tariffs are likely to rankle America’s allies like Canada and Mexico, which supply the bulk of U.S. metal imports. They could also elicit retaliation on U.S. exports, as well as pushback from American industries that use metals to make cars, food packaging and other products. Those sectors will face significantly higher prices after the tariffs go into effect.

That is what happened in Mr. Trump’s first term, when the president levied 25 percent tariffs on foreign steel and aluminum. While Mr. Trump and President Joseph R. Biden Jr. eventually rolled back those tariffs on most major metal suppliers, the levies were often replaced with other trade barriers, like quotas on how much foreign metal could come into the United States.

Studies have shown that while Mr. Trump’s first round of metal tariffs helped American steel and aluminum producers, they ended up hurting the broader economy because they raised prices for many other industries, including the auto sector.

The steel tariffs followed other intense trade threats. In his three weeks in office, the president has already threatened more tariffs globally than he did in his entire first term, when he imposed tariffs on foreign solar panels, washing machines, metals and more than $300 billion of products from China.

Since Jan. 20, Mr. Trump has put an additional 10 percent tariff on all products from China, and came within hours of imposing sweeping tariffs on Canada and Mexico that would have brought U.S. tariff rates to a level not seen since the 1940s. Together, those moves would have affected more than $1.3 trillion of goods.

Speaking from the Oval Office on Monday, Mr. Trump said his steel tariffs were “the first of many” to come. He said his team would be meeting over the next four weeks to discuss tariffs on cars, pharmaceuticals, chips and other goods.

Mr. Trump said on Sunday that he also planned to move forward this week with so-called reciprocal tariffs, which would raise certain U.S. tariff rates to match those of foreign countries.

American steelmakers welcomed the tariffs. In a statement on Sunday, Kevin Dempsey, the president of the American Iron and Steel Institute, said the group welcomed Mr. Trump’s “continued commitment to a strong American steel industry, which is essential to America’s national security and economic prosperity.”

But industries that use metals to make other products said overly broad protections would hurt them.

“Tariffs and other broad trade tools can make America great again, but there are unintended consequences for our nation’s food security when a tariff is placed on tin-plate steel,” said Robert Budway, the president of the Can Manufacturers Institute, which represents companies that make cans for fruits and vegetables.

The United Steelworkers union, which has members in Canada, said that it welcomed Mr. Trump’s effort to help the industry but that “Canada is not the problem.”

The new measures will mainly affect U.S. allies. The largest supplier of steel to the United States in 2024 was Canada, followed by Brazil, Mexico, South Korea and Vietnam, according to the American Iron and Steel Institute. Canada is also a major supplier of aluminum to the United States, followed distantly by the United Arab Emirates, Russia and China.

Late Monday, the governments of Canada, Mexico and Brazil had yet to respond to the tariffs. Brazil’s government said it did not have a response to Mr. Trump’s announcement of steel tariffs because it had not yet received any official communication from the U.S. government on the issue.

In his first term, Mr. Trump levied tariffs on foreign steel and aluminum using a national security provision called Section 232 of the Trade Expansion Act. That angered allies like Mexico, Canada and the European Union, which said they were not a security threat.

Mr. Trump used those tariffs as a negotiating tool. His officials reached agreements with Australia, South Korea and Brazil, and rolled back some of those barriers on Canada and Mexico when they signed a revised trade agreement with the United States. The Biden administration later reached agreements with the European Union, Britain and Japan to roll back some of their trade restrictions.

The United States imports very little steel or aluminum directly from China, since Chinese exports have long been blocked by a variety of anti-dumping and anti-subsidy tariffs. But some argue that China’s excess steel production is still flooding other markets and pushing down global prices, leaving U.S. metal makers at a disadvantage in other markets.

Brad Setser, an economist at the Council on Foreign Relations, said Chinese steel exports had basically doubled over the past two years and were creating economic issues globally as they flooded foreign markets, including in Asia and Latin America.

But Mr. Setser said he saw little evidence that Chinese steel was being routed into the United States through Canada or Mexico and undermining the U.S. industry.

“It’s pretty hard to make the case that the surge in Chinese exports globally has triggered a reduction in U.S. production,” he said. “U.S. production has been fairly stable.”

After Mr. Trump put steel tariffs into effect in 2018, U.S. steel imports steadily declined. But that trend reversed during the pandemic, when blast furnaces shuttered and supply chains seized up, and U.S. steelmakers were slower than competitors in Mexico to open back up, Mr. Setser said.

In the last few years, U.S. steel imports have been relatively flat, though they are slightly above the level when Mr. Trump imposed tariffs in his first term.

U.S. unions and major companies like Cleveland-Cliffs and U.S. Steel, which are influential with government, have argued that current protections are insufficient to keep them in business. Amid its financial struggles, U.S. Steel, the iconic Pennsylvania company, agreed to be acquired by Nippon Steel of Japan. That merger was blocked by Mr. Biden, who said he wanted to U.S. Steel to remain an American company.

Supporters of the tariffs have argued that the United States needs strong metal makers for its national defense.

Nazak Nikakhtar, a partner at the law firm Wiley Rein and an official in the first Trump administration, said the president was again “making good on his promise to impose tariffs globally and to increase tariffs on steel and aluminum imports, given their criticality to national security.”

But many economists argue that tariffs on raw materials like steel will hurt the economy, since they raise prices for other manufacturers.

A study by the nonpartisan International Trade Commission, for example, found that Mr. Trump’s earlier tariffs encouraged consumers of steel and aluminum to buy more American metals. The increase in demand pushed up metal prices and allowed American metal makers to expand, resulting in $2.25 billion of additional U.S. production of steel and aluminum in 2021.

But the tariffs also raised costs for industries that buy steel and aluminum to make other things, like industrial machinery, car parts and hand tools. Altogether, industries that consume steel and aluminum saw their production shrink by $3.48 billion as a result of the those higher costs — more than offsetting what the steel and aluminum makers had gained.

Other industries are concerned about being caught in the crossfire and targeted with tariffs as other countries retaliate. China imposed retaliatory tariffs on U.S. exports of liquefied natural gas, coal, farm machinery and other products on Monday in response to the tariffs Mr. Trump put on China last week because of its role in the fentanyl trade.

Mexico, Canada and the European Union have all drawn up lists of American products they could strike with their own levies in response to U.S. measures.

In response to Mr. Trump’s first metal tariffs, for example, the European Union imposed a 25 percent tariff on American whiskey. A deal negotiated by the American and European governments to suspend those tariffs is set to expire soon. If another agreement is not reached, the European Union is set to double that tariff to 50 percent on April 1.

Chris Swonger, the chief executive of the Distilled Spirits Council of the United States, said in a statement that the tariff would have a “catastrophic outcome” for 3,000 small distilleries across the United States.

“We are urging that the U.S. and E.U. move swiftly to find a resolution,” Mr. Swonger said. “Our great American whiskey industry is at stake.”

Colby Smith and Norimitsu Onishi contributed reporting.