Twenty-year-old Christopher Nkunku scored twice for Paris Saint-Germain at the Parc des Princes, with Thomas Meunier, Kylian Mbappe and Thiago Silva also on target.
Japanese goalkeeper Kawashima Eiji made several fine saves to avoid the visitors from being further behind for most part of the second half, but he could not stop PSG captain Thiago Silva's header on a corner with eight minutes remaining.
"Nobody can say that we didn't try, but this is football and although we have great players, Madrid showed us the difference between having great players and champions". "Digesting what happened is difficult but we are professionals, so we need to turn the page and move on".
It seems that the Qatari businessman has to make real changes in his team, starting with the Spanish coach, Unai Emery, who was offended by Parisian fans.
Mbappe was unable to get on the scoresheet in either game and the teenage wonderkid, who has netted 17 goals in all competitions this season, believes Real have a team of "champions".
After Meunier's opener, Nkunku put the game beyond Metz before the half-hour mark with two low finishes. He was denied a hat-trick goal before the interval for offside.
Second-placed Monaco won 3-1 at Strasbourg on Friday with Stevan Jovetic, Rony Lopes and Fabinho getting their goals.
Despite heavy investment over recent years - including the world-record €222milllion capture of Neymar - PSG have failed to make a significant impact in Europe, eliminated at the last-16 stage in the past two editions after four consecutive quarter-final appearances. Metz are bottom with 20 points, nine adrift of safety.
It was the same score between Dijon and Amiens at the Stade Gaston Gerard. Nantes moved to fifth, one point ahead of Rennes, who tied Saint-Etienne 1-1.