I’ll add my two cents, even though your question is VERY open and whatsmore important the title and content do no match. In general, French language is considered very fancy. See for instance this nice question

What languages are perceived as classy or fancy to French speakers?

and the answers therein (in particular user Matthieu M. reply). Why is it so considered?

(wiki) From the 17th to the 19th centuries, France was the leading power of Europe; thanks to this, together with the influence of the Enlightenment, French was the lingua franca of educated Europe, especially with regards to the arts, literature, and diplomacy; monarchs like Frederick II of Prussia and Catherine the Great of Russia could both not just speak and write in French, but in most excellent French. The Russian, German and Scandinavian Courts spoke French as their main or official language, regarding their national languages as the language of the peasants.

Moreover according to https://www.ef.com/wwen/blog/language/most-beautiful-languages-in-the-world/

If there is a language which draws a unanimous worldwide consent
regarding its beauty, it is French. (…) French has been described as smooth,
flowing, elegant and aesthetically pleasing. With its unpronounceable
“r”, its nasal vowel sounds “en”, “in”, “un” and melodious intonation,
it sounds extremely musical to the non-native ear. And let’s not
forget the strong cultural context which lends French the status of
the most beautiful spoken language in the world.

There is also a relevant Quora thread: Why is the French language seen as beautiful and upper class?

The beauty of the French language is, in my humble opinion, due to its capacity to be extremely logic – and yet, on the other hand, for being able to create precise painting-like content when used on a more intimate level.

French language is extremely precise. It may be used as a tool in philosophical argument, as well as be the core of a poetical composition. There is a subtle balance in French, and you may practically express every reasoning with clarity and elegance. It is mainly due to our use of “pronouns”, our various grammatical exceptions, tenses, the extensive use of “one’s” and our ability to generalize an example towards a concept.

As a consequence, it was a diplomatic language for many European countries – it enabled nobility ans scientists to discuss topics without the possibilities of misunderstanding. Mastering French let them be really precise about what they intended to say ; nevertheless, even a shady comment could be said so as to appear socially acceptable.

There are “different sorts of French” – but high French is mesmerizing. High French locutions, directly derived from Latin authors or from old Bible saying, offer a vast possibility for cultural collusions. Even more prosaic elements are labelled in a “romantic” way : a lampshade is, for us, a “day-humbler” (abat-jour).

French people use their language as a display of their culture. When a French intellectual finds an equal, he may use this language to quote references. The fascinating ramifications of French create several layers in the same speech : through this smooth level of subtleness, you can quote prominent French literature, and still be understood by the commoner. French are elitists – yet there are accessible. That’s pretty hard in other languages !

French has an elegant, whispering-like and vibrating sound. We do not use sounds that appear like noises. French is chanted, it has a rhythm and a precise movement. And even in our everyday life, we enjoy playing on sounds, puns, alliterations, metaphors… That’s mainly a sport.

Of course one can find in Internet a plethora of relevant staff. For instance

http://mentalfloss.com/article/74461/what-makes-french-sound-sexy

What Makes French Sound Sexy?

There’s just something about French, a certain je ne sais quoi that makes it widely considered to be the sexiest language in the world. The sensuality of the language, however, is not limited to spoken French itself; the French accent, in English at least, is excessively charming. The sex-appeal of this language knows no boundaries. But what is so sexy about French?