Vincent Lecavalier scored for Philadelphia (0-2-0), which was beaten 3-1 by Toronto in its season opener on Wednesday night. The Flyers play again Sunday night at Carolina.
Many of the 21,273 at the Bell Centre booed each time the puck went to Lecavalier, who turned down the Canadiens to sign with the Flyers this off-season.
It was Daniel Briere's first game against Philadelphia since the Flyers bought him out, but it was a quiet night for the veteran forward, other than taking two minor penalties.
The Flyers were victims of a quick whistle when Price lost a puck at his feet and Matt Read knocked it in, but it was ruled no goal.
Eller, who scored twice in a season-opening 4-3 loss to the Leafs, backhanded in the rebound of a Gallagher shot that missed the net only 12 seconds into the third frame.
A P.K. Subban shot looked to have gone in during a third-period 5-on-3 but video review found it went in the side netting. Only 18 seconds after play resumed, Subban faked a shot and passed to Galchenyuk, who slipped it to Gallagher for a 3-0 lead.
Next up for the Canadiens is a western road trip to Calgary, Edmonton, Vancouver and Winnipeg beginning Wednesday.
Notes: Max Pacioretty, who jammed a wrist in the season opener, did not dress. Brandon Prust took his spot on the top line and Michael Bournival made his NHL debut on the fourth unit. With George Parros out (concussion), Ryan White dressed. . . Plekanec played his 600th NHL game and defenceman Josh Gorges played his 400th, while the Flyers' Zac Rinaldo played his 100th. . . Nathan Beaulieu, called up Friday, did not dress. . . The Flyers scratched Erik Gustafsson, Kris Newbury and Hal Gill.