What happened

Shares of Stellantis (NYSE: STLA) opened sharply higher on Tuesday, the company's first day of trading in the U.S. Stellantis, the company formed from the merger of French automaker PSA Peugeot with Fiat Chrysler Automobiles. It had closed higher on Monday following its first day of trading in Europe. 

As of 11 a.m. EST, Stellantis's U.S.-traded shares were up about 11.4% compared to Fiat Chrysler's final closing price on Friday. 

So what

It's a done deal: Fiat Chrysler and PSA have merged to create the world's fourth-largest automaker. Now, CEO Carlos Tavares and his blended executive team have to make the combination work.

There's a lot of work ahead. The company owns a whopping 14 automotive brands, several of which have overlap with each other; most analysts expect at least a few brands to be cut as the automaker's sprawling product portfolio is consolidated. But the bigger picture -- fusing FCA's profitable SUV and truck brands with PSA's expertise in smaller vehicles and electrification -- is promising.

A silver 2021 Ram 1500 EcoDiesel, a full-size pickup truck.

Image source: Stellantis.

At least right now, auto investors seem to think that the company's chances of realizing the promised synergies are good, and that's why the stock is up Tuesday.

Now what

The plan in the United States seems clear: Under former Fiat Chrysler CEO Mike Manley, the company will seek to maximize the sales and profitability of its Jeep SUV and Ram truck brands. But the picture in Europe, where Fiat and Alfa Romeo and Citroen and Peugeot and Opel all compete for overlapping groups of customers, is much less clear.

I expect it will take at least a few quarters for Tavares and company to show gains from the combination. I also expect that we'll learn a lot more about the road ahead when Stellantis delivers its first post-merger earnings report, likely next month.