There was one lineup change for the game, with Justin Barron returning to action and Chris Wideman sitting in his stead. Sam Montembeault got the start in goal.
The Penguins opened the scoring early in the first, when Jake Guentzel buried a rebound to beat Montembeault just 21 seconds into the game.
Then, with Josh Anderson in the box for interference, Evgeni Malkin doubled his team's lead at the 4:49 mark of the first with a one-timer from near the faceoff dot to Montembeault's left.
But those pair of early goals gave the Canadiens a jolt of motivation, and they scored four unanswered goals before the period was up.
First, Mike Hoffman accepted a drop pass from Rem Pitlick and wristed it past Penguins starter Tristan Jarry for his 11th of the season just 32 seconds after Malkin's tally.
Pitlick and Barron earned the helpers.