Philip Dano also scored and Jake Evans added an empty-net goal for Montreal (35-18-10). Jakub Dobes made 17 saves.
William Nylander responded to Toronto’s (27-27-11) struggles as they face missing the playoffs after nine straight trips to the postseason.
Joseph Woll stopped 30 shots in a solid outing.
The Maple Leafs entered the night 11 points outside the playoffs and 13 points behind the Canadiens for the second wild card spot in the Eastern Conference.
Kapanen scored 4:46 into the first period, completing a slick passing play from Ivan Demidov and Alex Newhook to Deke at the goal line. Demidov blocked two Maple Leafs in the corner and sent the puck to Newhook, who fed Kapanen low.
Danault capitalized on a fortuitous bounce as Kaiden Guhle’s dump-in bounced off the glass and rolled in front of the Maple Leafs’ net to put the Canadiens up 2-0 at 14:41, gifting the veteran center his fifth of the season.
Nylander buried his 22nd goal on a give-and-go with Easton Cowan and got Toronto on the board at 14:33 of the second after a blast save by Dobes kept it a two-goal game under pressure from the Leafs.
Canadiens: In addition to working two shifts on the power play, Cole Caufield sat at the end of the Canadiens’ bench from late in the second period until the end of the game. Montreal’s leading goalscorer appeared to be in some discomfort, with trainers checking him occasionally, but it’s unclear when he sustained the injury.
Maple Leafs: The Canadiens dominated play early with the Leafs in the offensive zone, leading 2-0 after 20 minutes and outshooting the game 15-8. Toronto pulled away in the second period with Nylander taking the lead after Montreal missed several stacked opportunities, but Montreal stayed in the third.
Late in the first period, veteran Canadiens winger Brendan Gallagher got into a fight with Leafs defenseman Jake McCabe as the building exploded after interfering with Cowan.
Toronto captain Auston Matthews, a former 69-goal scorer, extended his scoreless streak to 12 games.
Maple Leafs: Host the Anaheim Ducks on Thursday.
Canadians: Visit the Ottawa Senators on Wednesday.
