* TSX gains 0.23 percent to 13,626.91
* Six of 10 groups down
* Bank of Montreal profit, stock rise
* Tim Hortons falls as CEO exits abruptly (Adds details)
TORONTO, May 25 (Reuters) - Toronto's main stock index climbed on Wednesday morning as rising metal prices and a firm start to bank earnings season outweighed persistent economic uncertainties.
Six of the index's 10 main groups were lower, but two of its weightiest sectors -- energy, and materials -- were up, keeping it in positive territory.
The price of copper rallied on tight supply, while gold drove to a three-week high, both spurring the materials group to rise more than 1 percent. The energy group rose 0.4 percent.
Fears about the debt crisis in Greece and other euro zone countries, which have created volatility in many of the index's resource issues, were put aside on Wednesday morning. Diversified miner Teck Resources TCKb.TO gained 1.7 percent to C$48.06, while Kinross Gold (K.TO) rose 0.8 percent to C$14.95.
"The next issue is commodities," said Paul Gardner, partner and portfolio manager at Avenue Investment Management.
"I think that's really the next thing to drop. We know Greece is in trouble and... (we'll) see if that has anymore follow through."
At 10:27 a.m. (1427 GMT), the Toronto Stock Exchange's S&P/TSX composite index .GSPTSE was up 31.79 points, or 0.23 percent, at 13,626.91, after opening slightly lower.
Bank of Montreal (BMO.TO) reported a rise in profit, bolstering hopes that the country's other big banks will also report solid second-quarter results. [ID:nN24268837]
"I wouldn't be surprised to see some not stellar, but strong numbers coming out of the banks, so that should settle down that part of the market," Gardner said.
Bank of Montreal rose 0.23 percent to C$61.64, though most of its peers were lower in choppy dealings. The financial sector was down 0.2 percent.
Tim Hortons THI.TO was one of the leading decliners, shedding 1 percent to C$45.36 after news that its chief executive had left the company abruptly. [ID:nL3E7GP270]
($1=$0.98 Canadian) (Reporting by Ka Yan Ng, Editing by Chizu Nomiyama and Peter Galloway)