Since neither @Laure or @Gilles wish to post an answer, I’m posting their comments until they want to or someone gives more informations :

@Gilles :
I think the distinction is that French, like English, has modal verbs as a grammatical function (e.g. I want to drink // je veux boire), but not modal verbs as a separate grammatical nature (there’s no equivalent of words like can and shall that don’t follow the usual rules such as third person singular -s ending, present participle formed by adding -ing, etc.

@Laure :
French has modal verbs. What you quote doesn’t say the opposite. I says ” Whether or not this is the case is a matter of opinion,”. Pouvoir & devoir are definitely modal verbs, there are a few others. Some grammarians call them semi-auxiliaires but they refer to the same thing.

More info : Pragmatique des verbes modaux en français : aspects synchroniques et diachroniques.

This is not an independent answer, but rather an addition concerning the practical aspect of modal verbs. From the point of view of a language learner (disclosure: English and French are both ‘second’ languages to me), the principal aspects of the modal verbs in English are:

• they are always followed by an infinitive
• they take infinitive without “to” (with some must-know exceptions)
• they form questions without an auxiliary verb

When studying French one confronts a rather different problem: whether and which preposition to use for introducing infinitive. In this respect devoir, vouloir and pouvoir are rather similar to modals, but there are many more verbs which behave in a similar fashion. Thus, the concept of a modal verb is not a very useful one.