Subban has 11 points in seven playoff games.
"I'm just the beneficiary of the guys playing well around me, supporting me," the defenseman said. "It starts in goal. Well, it actually starts with our coaching staff and making sure everybody is feeling confident. We're doing it together. ... When we had adversity, we're sticking together doing the right things.
"It's fun to play on teams where you know guys are going to support you."
Lars Eller and fourth-line winger Dale Weise also had a goal and an assist, and Tomas Plekanec scored Montreal's other goal.
Patrice Bergeron and Andrej Meszaros scored for the Bruins.
While Montreal has stolen home-ice advantage from the Bruins, the series between the longtime rivals is hardly over. Boston outshot Montreal 28-26, hemmed in the Canadiens in their end for long stretches, and looked nothing like a team that is overmatched.
But unlike the first two games, the Bruins were unable to erase a two-goal deficit. Their frantic third-period comeback fell short, and Eller ended it with an empty-net goal with three seconds left.
For the third straight game, the Canadiens held a 3-1 lead in the third period. This time, they didn't let it slip away. In Game 2 on Saturday in Boston, the Bruins scored four goals in the final 10 minutes for a 5-3 comeback win.
Chicago 4, Minnesota 0
St. Paul, Minn. • Erik Haula and Mikael Granlund scored goals less than 3 minutes apart early in the third period, and the Minnesota Wild recovered from a sluggish start for a 4-0 victory over the Chicago Blackhawks on Tuesday in Game 3 of the Western Conference semifinal series.
Ilya Bryzgalov made 19 saves for his first shutout in the playoffs in eight years, and the Blackhawks had their lead whittled to 2-1 with their first loss in 2½ weeks.
Game 4 is Friday in Minnesota.
• Montreal 4, Boston 2
Canadiens lead series 4-2
• Minnesota 4, Chicago 0, Blackhawks lead series 2-1
• Pittsburgh at N.Y. Rangers, 5:30 p.m., NBCSN
Penguins lead series 2-1