Merger news and corporate announcements were some of the catalysts behind the most actively traded stocks on Thursday.
Shares of metal mining companies were up sharply on news that Rio Tinto proposed a $38 million takeover bid for Canadian aluminum producer Alcan , topping a previous bid from Alcoa.
"The metal miners are the most active, but there's just not that many of those stocks around right now, you have Freeport-McMoRan, Rio, Alcoa and Alcan," said Tom Schrader, managing director of U.S. listed trading at Stifel Nicolaus.
Alcoa was the most actively traded stock in midday trading Thursday, rising 6%. Alcan shares rose more than 10% while Freeport-McMoRan jumped 6%. Shares of BHP Billiton, the world's largest mining company, rose 4%, while Century Aluminum rose more than 9%.
The head trader also said financial stocks showed strength on Thursday as worries regarding risks associated with the subprime mortgage market abated.
"My financials trader says it's the second day in a row they've been strong, so there is speculation that the subprime concerns have already gotten as bad as they are going to get," said Schrader.
Shares of financial giants Citigroup and JP Morgan Chase each gained more than 1% while Merrill Lynch rose 2.1%.
Investment banking firm Bear Stearns , at the center of recent industry concerns, gained 1.2%.
Semiconductor giant Intel led tech stocks higher with a gain of 5%, a new 52-week high.
Among downside movers, Whole Foods Market declined following news that Chief Executive John Mackey anonymously posted messages on a Yahoo stock message board defending his company and criticizing rival Wild Oats.
The Federal Trade Commission is attempting to block the pending merger with Wild Oats.
Bear Stearns research analyst Robert Summers said Thursday that the FTC has a solid case and maintained an "underperform" rating on Whole Foods.
"We believe the FTC case against the merger appears solid and are now leaning more toward the FTC prevailing in its injunction," Summers wrote in a client note.
Peter Kang is a markets writer at CNBC.com and can be reached at peter.kang@nbcuni.com.