The pressure on coach Unai Emery has been eased by an emphatic 5-0 victory over Lorient before the mid-season break and a 7-0 Coupe de France rout of Bastia at the weekend.
Though the margin of victory was not as emphatic this time around, PSG produced another dominant performance to suggest it is finding its rhythm ahead of the resumption of a Ligue 1 campaign that sees them surprisingly five points adrift of leader Nice.
And it was captain Silva who proved the difference maker in Thursday's contest at the Parc des Princes, the Brazil defender the only player able to beat David Oberhauser in the Metz goal.
Silva made it 1-0 in the 27th minute by turning home an Angel Di Maria corner, and the same formula paid dividends 18 minutes from time as PSG joined Monaco, Bordeaux and Nancy in the last four.
PSG dominated from the start and Edinson Cavani spurned a decent opening as he headed wide before Thomas Meunier hit the near post from a Di Maria corner.
And only the marvellous reflexes of Oberhauser prevented PSG from breaking the deadlock in the 17th minute.
Marco Verratti's exquisite diagonal ball was met by Christopher Nkunku, whose first-time cross found Cavani, only for the Uruguay striker to be denied by a fantastic reaction point-blank save from Oberhauser.
But Oberhauser could not prevent the hosts from opening the scoring 10 minutes later, Metz paying the price for some very poor marking.
Silva was afforded far too much space in the area and had the simplest of tasks to power another Di Maria delivery into the bottom-right corner.
An intricately worked move by PSG ended with Nkunku being denied at the near post by Oberhauser as Emery's men looked to put the tie to bed.
Oberhauser thwarted Jonathan Ikone a minute into the second half, and Metz continued to live extremely dangerously at the back.
Cavani's frustration was evident after he headed over a cross from Di Maria, who then became the latest player to see an effort kept out as he had a strike cleared off the line.
Metz improved after those scares and did threaten Alphonse Areola's goal, Habib Diallo curling narrowly over after an error from Presnel Kimpembe.
A busy night for Oberhauser continued, though, a wonderful passage of play between Adrien Rabiot and Di Maria going unrewarded as the latter saw his effort saved. Hatem Ben Arfa laid the rebound off to Cavani, whose attempt was kept out by the legs of Oberhauser.
But PSG did eventually double its lead as Silva's run again went untracked and he made no mistake in putting the game beyond doubt.
Former PSG striker Mevlut Erdinc went close to pulling one back and Cavani blazed over an acrobatic volley at the other end, but Emery and his players should go into Saturday's league meeting with Rennes in good spirits after 14 goals in their last three games.