Mbappe scored a hat-trick at the Parc des Princes following the announcement that he will continue to stay as PSG player next season.
The forward put his team ahead with a quick double in the first half, scoring in the 24th minute and again four minutes later before adding his third five minutes after the break.
Neymar scored a nice finish against Caillard between the Frenchman’s first two goals to increase their advantage.
Angel Di Maria also scored in what was his last game for the club, shortly after Traore was dismissed for his second yellow card.
Mauricio Pochettino’s team has gone unbeaten at the Parc des Princes this season, finishing with 86 points and now lifting the trophy.
Mbappe finished the season atop the Ligue 1 scorers and assists charts.
After being level on points with St-Etienne and having a decent goal difference before the game, Metz was desperately trying to avoid automatic relegation.
After St-Etienne sealed a draw with Nantes, Metz were left deep in the relegation zone and will now play in the second division next season.
PSG ended the season with a bang, winning the league title at the final whistle.