What is the proper use of “The” in front of certain nouns?

To me 'speaking the French' sounds wrong without adding 'language.' As far as I'm aware Jefferson Airplane have never used the definite article and to do so sounds a little quaint!

The Stranger was originally written in French, and the phrasing you see may be a translation artifact. I believe that French and some other Romance languages often use definite articles where they would not be used in English.

You do encounter the occasional unexpected exception to the "rules" suggested by other answers.

The Gambia. Not 'Gambia" even though this IS used.

In New Zealand "The North Island" and NEVER "North Island".
(Similarly "The South Island").

All of:
"The Christ".
"Christ".
"Jesus Christ".
"Jesus, the Christ".
(Caused by a title having been adopted as if it was a name)

"The bayou".
A bayou = generic term.
"The Bayou" - a specific (but unnamed) bayou.