The NL wild-card leaders moved a game ahead of the San Francisco Giants, who lost 1-0 at Philadelphia, as they started a 10-game homestand against losing teams with a much-needed win.
Jason Giambi made his Rockies - and National League - debut in the seventh when he batted for the pitcher with the bases loaded and drew a four-pitch walk from Sean Green.
All-Star third baseman David Wright was activated from the 15-day disabled list and played his first game for the Mets since getting hit in the head by a pitch from San Francisco's Matt Cain on Aug. 15. Wright went 1 for 3.
Wearing his bulky, new protective batting helmet, Wright helped New York take a 2-0 lead in a wild first inning when he singled and scored.
Jorge De La Rosa (13-9) settled down from his shaky start, though, and the Rockies took out Mets right-hander Mike Pelfrey (9-10) early, tagging him for seven runs, six earned, on six hits in four innings.
De La Rosa allowed just one earned run and four hits in six innings. He walked three and struck out six despite throwing exactly 50 balls and 50 strikes.
Carlos Gonzalez also homered for Colorado, his high drive slicing through the haze that meteorologists blamed on the California wildfires more than 800 miles away and landing in the second deck in right field.
Gonzalez's two-run shot off Pelfrey in the fourth gave Colorado a 3-2 lead and Helton added a run-scoring single before sending his 14th homer into the seats in right with two on in the fourth.
Back-to-back triples off Rockies reliever Matt Daley by Cory Sullivan and Angel Pagan in the seventh made it 7-3.
Pagan's baserunning gaffe cost the Mets an even bigger first inning.
After a leadoff single, Pagan advanced to second on Luis Castillo's one-hopper to center field but he thought Gonzalez had caught the ball on the fly and started sprinting back to first. After a few steps he realized his mistake but was thrown out, his blunder taking away Castillo's single on a play that was ruled a fielder's choice.
Wright put runners at the corners with a single and Jeff Francoeur lined out to Gonzalez, whose throw to the plate appeared to have a chance at nailing Castillo before hitting the pitching rubber and sailing over the head of catcher Yorvit Torrealba, allowing Castillo to score easily on the sacrifice fly.
Gonzalez was charged with an error because Wright advanced to second base on the wild hop, and he came around to score on a double by Fernando Tatis, making it 2-0.
The Rockies got a run back in the bottom half when Garrett Atkins drew a bases-loaded walk.
NOTES: Torrealba extended his career-best hitting streak to 11 games. ... Rockies SS Troy Tulowitzki was jammed in his first two at-bats, softly lining out to the pitcher and then bouncing to second baseman Castillo, who rushed to touch first base while Tulowitzki didn't bother leaving the batter's box.
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