Adam Gaudette scored an empty-net goal at 19:56 for the 7-5 final.
Oliver Kapanen gave the Canadiens a 1-0 lead at 6:18 of the first period with a wrist shot from the left circle that was deflected by Sharks defenseman John Klingberg.
Graf tied the game 1-1 at 15:32 with a backhand tap-in at the left post off a pass from Smith.
"He's just a really, really smart player. I've said a number of times. The way he thinks the game," Celebrini said of Graf. "His stick, he has such a great stick, turning over pucks and just making those little plays that maybe you guys don't even notice. He's just a great player and really smart."
Phillip Danault gave the Canadiens a 2-1 lead at 5:09 of the second period, deflecting Matheson’s shot from the left point.
Misa tied the game 2-2 at 10:28, scoring from the slot on a loose puck after Dobes tried to poke away the rebound of Tyler Toffoli’s shot.
Celebrini gave the Sharks a 3-2 lead at 18:23 with a wrist shot from the top of the left circle that beat Dobes through the five-hole.
Alexander Wennberg put the Sharks up 4-2 just 25 seconds later with a wrist shot from the slot at 18:48.
"A couple turnovers cost us tonight," Canadiens forward Josh Anderson said. "We battled back as a team. Look at a few things the next few days and get back to work."
The Sharks went up 5-2 on a power-play goal from Smith, who tapped in Celebrini’s pass from the right circle at the left post at 3:29 of the third period.
NOTES: Celebrini recorded his fifth career game with at least four points, passing Jimmy Carson (four) for the fourth-most by a teenager in League history, behind Wayne Gretzky (14), Crosby (eight) and Dale Hawerchuk (seven).