Guentzel's goal 21 seconds into the third made it 3-1 with the teams skating at 4-on-4. Kucherov made a backhanded pass from the end boards to a waiting Guentzel in front of the net.
It was Guentzel's 40th goal in 72 NHL postseason games.
"Best time to play, playoffs," Guentzel said. "There's really nothing better than Stanley Cup playoffs and being able to play in this. So you can't take it for granted. If you don't get up for these games, there's something wrong with you. It's just the best time of the year to play."
Glendening scored on a 2-on-1 off a pass from Yanni Gourde to give the Lightning a 4-1 lead at 14:19 of the third.
Cirelli scored an empty-net goal with Bobrovsky pulled for an extra skater for the 5-1 final at 15:00.
The Lightning had lost the first two games of the series at home, being outscored 8-2 in the process.
"You would have never known sitting in the locker room after Game 2 that we were down 0-2," Cooper said. "And so, riding into this game, it wasn’t going to guarantee the result, but I knew damn well how the effort was going to be. And they delivered."
NOTES: Kucherov is the seventh player in NHL history to have at least 30 multi-assist games in the playoffs. Wayne Gretzky leads all players with 72 such games. It was Kucherov's 11th three-assist playoff game in the postseason to tie Paul Coffey and Doug Gilmour for third-most all time. Gretzky did so 28 times, and Mark Messier 12. ... Tkachuk scored his 20th playoff goal with the Panthers. He ranks behind Carter Verhaeghe (26) and Sam Reinhart (22) for most playoff goals in team history. ... Florida lost for just the fourth time in 25 playoff games since 2023 when scoring first.