• Investors are hoping for a Santa Claus rally during the shortened trading week.
• MicroStrategy shares are up 477% this year, thanks to the rise of bitcoin.
• Japanese automakers Nissan and Honda are officially in talks to merge.

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

1. Holiday hopes

Is that you, Santa Claus? Trading is expected to be muted during the shortened holiday week on Wall Street, but investors are hoping stocks will end the year on a high note, thanks in part to the Santa Claus rally. That rally period covers the final five trading days of the year and the first two in January. Since 1969, the S&P 500 has added 1.3% in that stretch, on average. The New York Stock Exchange will close at 1 p.m. Tuesday for Christmas Eve, and the market will be shut on Wednesday for Christmas Day. Follow live market updates.

2. Let's talk

Japanese automakers Nissan and Honda officially entered merger talks on Monday as the industry deals with fierce competition for electric vehicles and other new technologies. If the two companies go through with a tie-up, it would create the world's third-largest automaker by sales. Mitsubishi, Nissan's strategic partner, has been offered the chance to join the new group and will make a decision by the end of next month. Honda CEO Toshihiro Mibe said the two would share resources, but both brands would be protected.

3. Wrapped up

Congress passed a stopgap spending bill over the weekend, and President Joe Biden signed it on Saturday, averting a government shutdown after a chaotic, high-stakes week in Washington, D.C. The bill will keep federal government spending at current levels for three months and will provide additional disaster relief and farm aid. Tesla CEO Elon Musk and President-elect Donald Trump both criticized an initial 1,500-page funding plan, effectively killing it and leading to the last-minute scramble, prompting criticism from Democrats.

4. Red and green

MicroStrategy has ridden a "red sweep" in politics to a strong year on the stock market. The company has been building its bitcoin reserves for years, and until this year was one of the few ways institutions could buy bitcoin. It's surged with the price of bitcoin, and the rally intensified after Donald Trump won the presidential election in November. The company's shares are up 477% this year as of Friday's close, second to only AppLovin among all U.S. tech companies valued at $5 billion or more, according to FactSet data. "I think the election year has inspired the crypto community to find its voice, and I think it has catalyzed a lot of enthusiasm that was latent," MicroStrategy founder Michael Saylor told CNBC.

5. Looking to the new year

It's an annual CNBC tradition: Reporter Alex Sherman asked media executives for their predictions on what 2025 will bring the business. Thirteen executives spoke anonymously and candidly about what they think will happen next year as the industry goes through a transition and consumers keep cutting cable. Their predictions range from speculating about Disney CEO Bob Iger's succession to the future of Comcast and The Washington Post. Read the full list of media predictions here.

— CNBC's Yun Li, Jenni Reid, Christina Wilkie, Laya Neelakandan, Lora Kolodny, MacKenzie Sigalos, Ari Levy and Alex Sherman contributed to this report.