• President Biden is set to join UAW workers on the picket line.
• A departing top Amazon executive will lead Jeff Bezos' Blue Origin.
• Apple's Eddie Cue is set to take the stand in the Google antitrust trial.

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

1. A brief reprieve

September has lived up to its sullen reputation for stocks. Markets finished in the green Monday, snapping a four-day losing streak for equities, but we're still headed for a losing month. Futures looked glum Tuesday, at that. The quarter is winding down, too, so that means earnings season will begin in earnest in just a few weeks. On Tuesday, investors will also get a look at the Conference Board's freshest read on consumer confidence, as well as new home sales data. In Washington, meanwhile, the threat of a government shutdown in just a few days is growing as majority House Republicans struggle to reach an agreement on a bill. Follow live market updates.

2. Politics and picket lines

With no end in sight to the United Auto Workers' strikes against the Detroit automakers, things are about to get a lot more political. President Joe Biden is slated to head to Michigan on Tuesday to join workers on a picket line. UAW President Shawn Fain is expected to join Biden, who has said auto makers should pay up after making big profits. The UAW has yet to endorse Biden, however. Former President Donald Trump, likewise, has sought to exploit divisions within the union's ranks. Trump, who is on track to challenge Biden next year, is headed to Michigan on Wednesday for his own rally. The White House, meanwhile, said Trump's plans didn't force Biden's hand. "This decision to visit the picket line was based on his own desire. This is what the president wanted — to stand with autoworkers," press secretary Karine Jean-Pierre said.

3. Space shakeup

Jeff Bezos' Blue Origin will have a new CEO by the end of the year. On Monday, the Amazon founder's space comany told employees that Bob Smith would be stepping down come December, when he'll be replaced by departing Amazon executive Dave Limp. Bezos, when he was CEO of Amazon, worked closely with Limp on several key projects, including Alexa and the company's Project Kuiper internet satellite initiative. The shakeup comes as Blue Origin tries to play catchup with Elon Musk's SpaceX, which has become the dominant player in the launch market.

4. Apple on the stand

One of Apple's most influential executives is headed for the stand Tuesday as the Justice Department tries to nail Alphabet's Google for using licensing deals to monopolize online search. Eddie Cue, Apple's senior VP of services, is expected to testify that his company uses Google search as the default option on its iPhones because it is the best option. Cue negotiated the deal for Apple. Google pays Apple billions of dollars for that right. This year alone, analysts say it could amount to $19 billion. It's one of the most prominent agreements in the tech industry, and much of its details are otherwise shrouded in mystery, even as the government puts it on trial.

5. The show must go on

While the showbiz world waits for details about the Writers Guild of America's tentative, strike-ending deal with Hollywood studios, investors lifted the stocks of movie theater companies. Shares of AMC, Cinemark and IMAX all finished higher Monday on the heels of the announcement. Hollywood's not out of the woods yet, though. The writers still need to ratify the agreement, while the actors' strike continues, effectively keeping productions shut down for the time being. Elsewhere, SAG-AFTRA, the union that represents actors, is gearing up for another potential work stoppage – this time in the video game industry, as voice actors and motion capture performers overwhelmingly voted to authorize a strike.

– CNBC's Brian Evans, Emma Kinery, Michael Wayland, Morgan Brennan, Michael Sheetz, Kif Leswing and Drew Richardson contributed to this report.

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