Is this passive voice?

Question

In the sentence, "je plais à Luc", it would seem that "je" would be the subject and "Luc" the object, but in the translation, "Luc likes me", that is turned around and "Luc" is the subject and "me" the object. So the english translation doesn't feel passive but the french does.

Answer

Bonjour James,
Let me see if I can help answer this one for you or at least provide some insight.
In the phrase «je plais à Luc» -->  I am pleasing to Luc or I please to Luc (awkward phrase).  
Here is the lesson explanation in part:
In French, you actually say plaire à [quelqu'un] (lit. to be pleasing 'to' [someone])
Le chocolat plaît à Martha.
Note that the verb agrees with the object - the person or thing being liked, not the person who likes.
One quick story here:  When I traveled to Rouen, I had a guide whom I like a lot and she gave us  very useful historical information.  So at the end of the day trip as I was handing her the tip I told her:  Votre présentation me plaît beaucoup, c'était très intéressante et instructive. (actually, I should have stated «m'a plu beaucoup»).  The take-away is this, I was telling her that her presentation was pleasing to me a lot.  But in French the correct syntax is:  
Votre présentation me plaît beaucoup -->  Your presentation is pleasing to me.  
This is another example of a verb where the syntax changes like the verb «manquer à» but that is another lesson.
J'espère que ma réponse vous aidera bien.

Answer

"Je plais à Luc" is literally translated as "I please Luc".
Je = subject
plais = verb (first person singular of plaire)
à Luc = indirect object.

The problem arises when you translate this sentence into proper English. You would say "Luc likes me" and here the roles of subject and indirect object are reversed. But this is due to the verb "like" which takes these things in opposite order and NOT due to the French being in passive voice.

-- Chris (not a native speaker).