Brendan Gallagher had a goal and two assists and the Canadiens beat the Blues 6-3.
Tomas Tatar, Jonathan Drouin, Philip Danault, Arturri Lehkonen, and Max Domi also scored for Montreal.
''We had a good game today,'' Danault said. ''We had the Stanley Cup champions so it was a good challenge for us,''
Drouin was awarded his team's player of the game award, a sword replica from the Arnold Schwarzenegger movie ''Conan the Barbarian.''
''Last year we had the cape. This year it's the sword. It's a new tradition,'' Drouin said.
Brayden Schenn, Samuel Blais, and Vince Dunn scored for St. Louis, which absorbed its first regulation loss of the season.
''They played better, they played harder than us,'' Blues head coach Craig Berube said.
Montreal goalie Carey Price made 26 saves. Jordan Binnington stopped 31 shots for the Blues.
The Canadiens earned their first regulation victory of the season.
Montreal head coach Claude Julien gave his players the day off from skating Friday but had his players watch video to prepare for the Blues.
''We're fortunate enough that two (of our games) were at home,'' Julien said. ''These guys use a lot of energy night after night. They get on the plane, they get back home at one in the morning. They've got to play the next night. It's not easy, but you have to manage it,''
Tatar tipped a bouncing puck past Binnington in the first-period to open the scoring. It was his second goal of the season.
Schenn tied the game 1-1 with 2:03 left in the period, firing a shot that banked off the inside post past Price.
Less than a minute later, Drouin responded with a goal of his own. He skated into the offensive zone and fired a shot past Binnington as two Blues defenders closed in. Drouin has at least a point in each game he's played this season.
The Blues tied the game in the second period when Blais scored a goal off a tight angle.
Dunn made it 3-2 by scoring a power-play goal 11 minutes later.
St. Louis' advantage lasted less than three minutes. Danault tied it at 15:35 of the second period.
Lehkonen scored the eventual winner for Montreal at 7:30 of the third period. He wrapped around Binnington and jammed the puck underneath the goalie's left pad, stabbing at it until it went in the net.
Gallagher and Domi added insurance goals in the third.
''We had it 3-3 going into the third,'' Schenn said. ''Didn't bring out our best effort in the third. We turned over pucks and they just wanted it more than us in the third period.''
Blues: At Nassau Coliseum to face the New York Islanders on Monday.
Canadiens: Host the Tampa Bay Lightning on Tuesday.
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