• Trump hosted the CEOs of Walmart, Target and Home Depot to talk tariffs.  
• Tesla reports earnings after the bell Tuesday.
• Harvard is taking the Trump administration to court.

Here are five key things investors need to know to start the trading day:

1. Another leg lower

The Dow Jones Industrial Average fell nearly 1,000 points Monday, or roughly 2.5%, as several new signals shook traders' confidence. President Donald Trump ratcheted up his anger toward Federal Reserve Chairman Jerome Powell, demanding in a Truth Social post that the central bank lower interest rates "NOW." Investors are also searching for progress in U.S. trade negotiations, but not finding much. With the Dow down, the S&P 500 lost 2.36%, and the Nasdaq Composite shed 2.55%. Follow live markets updates.

2. Trade meeting

Trump hosted retail leaders at the White House Monday to talk tariffs. The CEOs of Walmart, Target and Home Depot met with Trump in what the companies called a productive meeting. The big-box companies are in the crosshairs of Trump's trade policies, with tariffs poised to raise costs for retailers and consumers. "More tariffs equal more anxiety and uncertainty for American businesses and consumers," said David French, executive vice president of government relations at the National Retail Federation, in early April. "While leaders in Washington may not care about higher prices, hardworking American families do."

3. Road signs

Tesla reports earnings after the bell Tuesday. The EV maker's performance has been in the spotlight in recent months as CEO Elon Musk lent his attention to government efficiency efforts. Analysts project revenue growth of less than 1% for the first quarter. It would come on the heels of a 13% decline in deliveries for this period, which Tesla reported in early April. Wall Street will also be looking for answers on Tesla's tariff impact. The company relies on suppliers in Mexico and China for certain car parts. Tesla shares have lost almost half their value since Trump took office in January.

4. Capital injection

Roche is investing $50 billion in the U.S. over five years to stand up stateside research and production, the company said Tuesday. The Swiss pharma giant said the effort will create more than 12,000 jobs and signals its "long-standing commitment to research, development and manufacturing in the US." It's the latest example of foreign investment in the U.S. under the current Trump administration and comes as Trump threatens to put sectoral tariffs on the pharmaceutical industry.

5. Someone call Elle Woods

Harvard is taking the federal government to court. The university sued the Trump administration on Monday after the government said it would freeze $2.2 billion in grants over demands to audit the Harvard study body for "viewpoint diversity." The lawsuit was filed in federal district court in Massachusetts (Harvard is just outside Boston) and accuses the government of disregarding the First Amendment. "The consequences of the government's overreach will be severe and long-lasting," Harvard President Alan Garber said Monday.

– CNBC's Lisa Kailai Han, Sean Conlon, Kevin Breuninger, Megan Cassella, Melissa Repko, Ari Levy and Chloe Taylor and NBC News contributed to this report.