• Stock futures fell again Monday, after the S&P 500 had its worst week in months amid fears about President Donald Trump's tariff policy.
• Mark Carney won the race to replace Justin Trudeau as Canada's prime minister, as the country tries to navigate a trade war with the U.S.
• Novo Nordisk shares fell as trial results for the company's next-generation weight loss drug fell short of expectations.

Here are the most important news items that investors need to start their trading day:

1. Woeful week

U.S. stock futures dropped again Monday, after chaos around President Donald Trump's tariff plans sent markets tumbling last week. The S&P 500 is coming off a 3.1% drop, its worst week since September. The Dow Jones Industrial Average and Nasdaq Composite fell 2.4% and 3.5% last week, respectively. Concerns around Trump's trade policy, and its potential to raise prices and drag on economic growth, could weigh on markets again this week. Two surveys this week from the New York Fed and University of Michigan will offer readings on how consumers feel about the economy. Inflation data will also drive stocks this week: the February consumer price index is due Wednesday, followed by the producer price index Thursday. Follow live market updates.

2. Trade tumult

Trump last week imposed 25% tariffs on imports from Canada and Mexico, then suspended duties on many goods after frenzied negotiations with the two U.S. neighbors. He also put 10% duties in place on Chinese goods. The tariffs are set to escalate this week, as Commerce Secretary Howard Lutnick told NBC's "Meet the Press" that 25% levies on steel and aluminum imports are set to start Wednesday.  Meanwhile, the Trump administration has said reciprocal tariffs on countries that impose duties on U.S. goods will take effect April 2. As those policies raise fears that households will face higher costs and the economy could tip into a recession, Trump appeared to acknowledge Sunday that his trade plans could drag on the economy in the near term. "There is a period of transition because what we're doing is very big. We're bringing wealth back to America. That's a big thing," he told Fox News's "Sunday Morning Futures."

3. On the Mark

Mark Carney won the race to replace Justin Trudeau as Canada's prime minister, at a time when backlash to Trump's tariffs has inflamed national pride in the country. Carney, a relative political newcomer, cast himself as the best candidate to succeed Trudeau during the economic conflict because of his experience leading Canada and England's central banks. Trudeau had imposed retaliatory tariffs on U.S. goods, at a time when many Canadian retailers also pulled U.S. products off their shelves in protest. "My government will keep our tariffs on until the Americans show us respect," Carney said.

4. Shutdown showdown

The risks to the U.S. economy don't end with trade. If Congress fails to pass a funding bill by Friday, the federal government will shut down. House Republicans released a plan over the weekend that would keep the government running through Sept. 30, but Democrats will likely oppose it because it would reduce nondefense spending below 2024 levels. If the government shuts down, it could lead to worker furloughs and service disruptions at a time when Elon Musk's so-called Department of Government Efficiency has carried out mass federal layoffs.

5. Novo disappointment

Novo Nordisk shares fell on Monday as trail results for its next-generation weight loss drug fell short of expectations. The treatment, CagriSema, helped obese or overweight adults with Type 2 diabetes lose 15.7% of their body weight after 68 weeks. However, that weight loss was not as much as the 25% the Danish drugmaker previously anticipated. The results come as Novo Nordisk and U.S. drugmaker Eli Lilly, the two dominant players in the booming weight loss drug space, try to gain an advantage with new medications that could be more effective or convenient. Novo Nordisk aims to file for regulatory approval for CagriSema in the first quarter of next year.

– CNBC's Jesse Pound and Chloe Taylor, and the Associated Press and Reuters contributed to this report.