Also scoring in the Capitals onslaught were Boyd Gordon, Brooks Laich and Eric Fehr, as Washington broke the game open for a 4-0 lead, chasing starting goalie Jaroslav Halak and taking the advantage in the best-of-seven series.
Laich and Fehr added helpers and Matt Bradley chipped in with a third-period goal while 21-year-old goalie Semyon Varlamov turned aside 26 shots in the win, including 10 in the first period when he robbed the Canadiens on several chances.
Varlamov started in place of Jose Theodore, who was pulled during a shaky Game 2.
Tomas Plekanec got the only goal for Montreal. After Halak was pulled, Carey Price came in to stop 21 shots in relief.