* TSX down 0.2% at 21,587.880

* Posts lowest closing level since March 5

* Materials sector declines 0.5%

* Primo Water shares gain after merger deal

June 17 (Reuters) - Canada's main stock index fell to a three-month low on Monday as its heavy weighting in resource shares and low exposure to technology proved unattractive to investors even as Wall Street extended its record-setting run.

The Toronto Stock Exchange's S&P/TSX composite index ended down 51.22 points, or 0.2%, at 21,587.88, its lowest closing level since March 5.

In contrast, U.S. benchmark the S&P 500 notched an all-time closing high, helped by its heavy weighting in high-flying technology shares.

"The TSX, it's just missing the ingredients," said Barry Schwartz, a portfolio manager at Baskin Financial Services. "We just don't have the right businesses for this type of economy."

Tech shares account for just 11% of the TSX's market capitalization, while financial and resource shares combined have a roughly 60% weighting.

The materials group, which includes metal miners and fertilizer companies, fell 0.5%, as gold and copper prices fell, while energy ended 0.1% lower.

The high-dividend paying utilities group lost 0.9% as bond yields clawed back some recent declines.

One bright spot was the industrials sector, It added 0.6%, while consumer staples ended 0.4% higher.

The consumer-related sector was helped by a gain of 2% for the shares of Primo Water Corp after the packaged water company entered into a merger agreement with BlueTrition Brands. (Reporting by Fergal Smith in Toronto and Nikhil Sharma and Purvi Agarwal in Bengaluru; Editing by Shreya Biswas and David Gregorio)