The Stade de France is outside the city (not within the 75 postal code anymore). Basically, in the middle of nowhere towards the CDG airport. But still, it has an outstanding architecture by famous Jean Nouvel (Institut du Monde Arabe, Musée du Quai Branly etc).
I suggest you have a nice late lunch and get some sandwiches or other goodies to take along. The sandwiches, etc. at the Stade de France are truly awful and expensive for what they are.
I made the mistake of getting one recently at the Rolling Stones gig and couldn't finish it, because it was inedible like most of the food they sold at the stands outside the stadium.
If you should be hungry once back in the city, do treat yourself with a nice night cap and a snack at any cozy place near your hotel.
Enjoy the show.