John Carlson, Tom Wilson and Nic Dowd scored for the Capitals (41-23-10), who had won four straight. They fell five points behind the Pittsburgh Penguins for third place in the Metropolitan Division and remained three points behind the Boston Bruins for the second wild card into the Stanley Cup Playoffs from the Eastern Conference. Ilya Samsonov made 15 saves on 19 shots before being replaced by Vitek Vanecek, who made 10 saves.
"From the start there, they were coming out harder," Washington center Nicklas Backstrom said. "They were first on pucks and we weren't really there, I think. It's one of those games you want to forget."
Bunting put the Maple Leafs ahead 1-0 at 4:37 of the first period with a one-timer from just below the left hash marks off a pass from Mitchell Marner. Matthews got an assist, picking the puck off the sideboards and getting it to Marner with a pass between his legs for his 100th point.
It was Bunting's first goal in 18 games.
"It felt good," said Bunting, who had 12 assists during the goal drought. "Obviously I was a little dry there for a little bit, but that's hockey. There's ups and downs and you can't get too low on the lows. It felt good to get one in, but more importantly [Matthews] got his 100th point there, so that was a pretty special moment for the whole team.
"Anybody who says (the goal drought) isn't (weighing on you) is probably lying, so obviously it was in my mind a little bit, but we were winning and my line was producing and we were going really well, so I couldn't let that get in my way of playing my game."
Nylander made it 2-0 with a slap shot on the rush at 13:34 after taking a stretch pass from Pierre Engvall.
Carlson cut it 2-1 at 10:08 of the second period when he got around Toronto defenseman Jake Muzzin, cut to the net and scored around Campbell's outstretched left pad.
Ilya Lyubushkin gave the Maple Leafs a 3-1 lead at 10:19 with a slap shot from just inside the blue line. It was his first goal in 23 games with the Maple Leafs since being traded from the Arizona Coyotes on Feb. 19 and his second goal in his 203rd NHL game.
"The guys were pumped, yeah, the guys were excited, the fans were excited," Keefe said. "That was pretty cool for him. He's played really well for us. His family has just come into Toronto, they'd been in Arizona for a long time and they just got back here, it was the second game they'd been here. For him to score tonight and continue to play well, we're happy for him."
Nylander pushed the lead to 4-1, tapping in a puck on the goal line at the left post 18 seconds later at 10:37. Samsonov was pulled immediately following the goal.