L.A.’s Reliance Steel & Aluminum Co. has agreed to acquire Metals USA Holdings Corp. for about $766 million in a deal that will add 48 distribution centers for Reliance in the United States.

Reliance, the largest metals service center company in North America, will pay $20.65 a share for Metals USA, which is headquartered in Fort Lauderdale, Fla., the companies said in a joint statement Wednesday. The acquisition was the biggest in Reliance’s history. New York asset management firm Apollo Global Management LLC currently owns about 53 percent of Metals USA.

Shares of Reliance rose 8.6 percent to $70.25, the highest price since 2008. the company’s stock has risen 28 percent in the last 12 months. Shares of Metals USA jumped 13 percent to $20.65.

“We believe that the combined company will be well positioned to continue to outperform the broader metals service center industry,” said Reliance Chief Executive David Hannah.

The deal, which has an enterprise value of $1.2 billion, is expected to close in the second quarter of 2013.