What happened

Shares of T-Mobile (NASDAQ:TMUS) climbed by 6.5% on Friday, following the wireless-network operator's strong second-quarter results. 

So what 

T-Mobile continues to enjoy some of the best growth in the U.S. telecom industry. It added more than 1.2 million net new customers in the second quarter. This figure includes 1.1 million postpaid subscribers, who pay monthly bills and are generally the most profitable and sought-after wireless customers.

Thanks to its blockbuster merger with Sprint, T-Mobile's total customer base now stands at 98.3 million, which places it ahead of AT&T (NYSE:T) and behind only Verizon (NYSE:VZ).

A person is pointing to an upwardly sloping chart.

T-Mobile stock rose sharply on Friday. Image source: Getty Images.

The merger with Sprint also led to strong growth in T-Mobile's key financial metrics. Revenue surged 59% to $17.7 billion, while its adjusted earnings before interest, taxes, depreciation, and amortization (EBITDA) soared 91.5%, to $7 billion.

Now what

If T-Mobile is to overtake Verizon, it will need to invest heavily in its new 5G network. That spending is likely to weigh on its near-term profits and cash production. But if T-Mobile can build a best-in-class fifth-generation network, the hard-charging company could eventually earn a place atop the wireless-subscriber rankings.

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