Metz, which in French is pronounced approximately like the English word mess (but with a different vowel sound, in French it’s open-mid front unrounded and in English it’s close-mid front unrounded, okay?), is a city of 124,000 people on the Moselle River.
Their opera house, the Opéra-Théâtre on Place de la Comédie, was built between 1738 and 1753. It is said to be the oldest theatre in France that is still functioning as such.

Opéra-Théâtre, Place de la Comédie, Metz
If you want to see an opera there you will have to schedule your visit carefully, because they only do five opera productions each season, with three performances of each. That makes fifteen performances per year — not exactly a hotbed of operatic activity.
Just for comparison, the Frankfurt Opera did eighteen performances of six different operas that same month, April 2006. Of course Frankfurt is five times as big as Metz, so the difference is understandable, still you should know that you can’t just breeze into Metz any old time and expect them to be performing an opera that same evening.
Typically each opera in Metz is performed on a Friday, a Sunday and a Tuesday evening. When I was there I went to the Tuesday performance because the other two were sold out, at least that’s what it said on their website.

Opera poster
The opera I saw on that Tuesday evening was Les liaisons dangereuses by Claude Prey (1925-1998), a 20th century French composer whom I must admit I had never heard of before. The opera is based on a celebrated 18th century novel of the same name, by Choderlos de Laclos (1741-1803).

Program booklet for Les Liaisons Dangereuses
Both the novel and the opera are about the mores (not morals because they didn’t have any) of a certain kind of decadent French aristocrats in the bad old days before the French Revolution. These folks were contemporaries of the Marquis de Sade (1740-1814), from whose name the word sadism was derived. Their idea of a good time was to seduce people they considered particularly virtuous, and lead them into a life of debauchery. One of the characters, the Vicomte de Valmont, accomplishes this twice during the opera.
There are five singers in this opera and five musicians, who play on 18th century instruments. Each musician is supposed to have a particular relationship to a particular singer, but I’m afraid this aspect was lost on me.

Inside the Opéra-Théâtre during the intermission
I was curious to hear what kind of music a 20th century composer would write for 18th century instruments to tell an 18th century story. My impression, on first listening, was that the music was quite harmless, meaning it did not grate on the ears but also did not make any particular impression. Perhaps if I were to hang around French opera houses more often I would develop more of an ear for this sort of thing, I don’t know.

Looking down, during the intermission
Since this is such an elegant 18th century theater, my expectation was that people in the audience would be dressed in some elegant way to match the décor. But no, the dress code was a resounding “come as you are”. For a long time I thought I was going to be the only one wearing a tie, but then shortly before curtain time two or three other men in suits and ties rushed in, having come straight from work presumably. Otherwise there were lots of young people dressed to impress each other but not their elders, and a bunch of folks who looked just plain scruffy. Hardly anybody had entrusted their coats to the nice old ladies out in the cloakroom. The house was maybe three-quarters full, so there were enough empty seats for people to drape their coats over.
Oh, and upstairs there were maybe eight or ten young people in the audience wearing spiffy blue uniforms of some sort. To me they looked like the Salvation Army, but I expect they were something more prestigious than that.
The house really does have an 18th century feel to it, with unusually shallow steps on the staircases for instance, but the stage machinery is modern. There is a revolving stage which was put to good use during the performance.
By the way, they also do plays and operettas here sometimes, not just the fifteen opera performances per year.

The upper lobby
The upper lobby is a bit stuffy, but has an appropriately 18th century look and feel to it. (And smell, but maybe that was just my imagination.)
My photos in this post are from 2006. I revised the text in 2018.
See also: Operas in Koblenz, Germany. Koblenz is 304 km downstream from Metz
on the Moselle River and also has a beautifully renovated 18th century opera house.
Ah, Metz. My favourite French City