"I'll have to bug [Gorges] about that," Gallagher said. "I know how good he is blocking shots. It's not easy to get pucks by him. Fortunately I found a hole and it went in, but he's pretty good at getting in the way of pucks. It's nice to have to something to bug him about, I guess."
After Sabres left wing Matt Moulson made it 2-1 with a power-play goal 35 seconds into the third period, Gallagher made it 3-1 at 6:43 when he tipped a wrist shot from the blue line by defenseman Shea Weber past Lehner.
Weber made his Canadiens debut after he spent 11 seasons with the Nashville Predators. He was acquired from Nashville in a trade that sent defenseman P.K. Subban to the Predators.
"I thought [Weber] had a solid game," Montreal coach Michel Therrien said. "He was good offensively, put the puck on the net for the Gallagher goal, but I thought defensively he was really, really solid out there."
The Canadiens have won three straight season-opening games. The Sabres have lost four straight openers.
Montoya, who signed with the Canadiens as an unrestricted free agent on July 1, replaced Price, who has the flu.
"A bit of nerves coming in, and it's always sweet to play that first game for your team," Montoya said. "You just hope to give them a chance, and that's all my plan was. I wasn't trying to steal the game; I've got a good team in front of me."
Torrey Mitchell made it 2-0 3:21 into the second period when he poked a rebound of Paul Byron's shot between Lehner's legs. Andrew Shaw, another new Canadiens player, made it 4-1 with 8:24 left in the third period when he put a loose puck through Lehner's pads. Sabres coach Dan Bylsma challenged the call and claimed Lehner was interfered with, but after video review the call on the ice was upheld.