Stock market has its best day since early April

The stock market closed up more than 3% on Monday — the biggest rally in over a month — amid news that Moderna's phase one coronavirus vaccine trial showed a positive first step.

Why it matters: The stock market has rebounded in recent weeks in the face of the coronavirus crisis, which has pushed the U.S. economy into the worst downturn since the Great Depression. Long-time investors have warned about stocks' high valuations based on optimism about a vaccine or cure, as well as the economy's ability to fully rebound.

The big picture: Congress passed coronavirus relief to support workers and small businesses during the economic lockdown. Another stimulus package passed the House, but faces opposition in the Senate.

• The Federal Reserve has also taken unprecedented steps to launch lending facilities to shore up the economy — and more support could be coming.
• "There's really no limit to what we can do with these lending programs that we have," Fed Chairman Jerome Powell told 60 Minutes last night, an interview that some traders said helped optimism on Wall Street.

By the numbers:

• The S&P 500 rose 3.1%.
• The Dow Jones Industrial Average jumped 911 points (or 3.8%).
• The Nasdaq Composite climbed 2.4%.