How to Translate Modal Verbs into French

Modal verbs, also called modal auxiliaries or simply modals, are unconjugated English verbs which express the mood of a verb, such as ability, possibility, condition, and necessity. With the exception of "ought," modals are followed directly by the verb they modify (without "to" in between). There are ten common English modal verbs:

1. can
2. could
3. may
4. might
5. must
6. ought to
7. shall
8. should
9. will
10. would

French does not have modal verbs, which can make it difficult to translate them. The French equivalents of modal verbs may be a conjugable verb (e.g., pouvoir), a particular verb tense or mood, or even an adverb.

Can =  pouvoir, savoir (in the present tense)

   I can help you.
Je peux vous aider.
We can see it.
Nous pouvons le voir.
Can you swim?
Sais-tu nager ?

Could (in the present) =  pouvoir (in the conditional)

   I could dance all night.
Je pourrais danser pendant toute la nuit.
Could you help me?
Pourriez-vous m'aider ?

Could (in the past) =  pouvoir (in the imperfect)

   He could eat a lot of candy when he was three.
Il pouvait manger beaucoup de bonbons quand il avait trois ans.
Last year, I could sleep until noon every day.
L'année dernière, je pouvais dormir jusqu'à midi tous les jours.

May/might = peut-être, pouvoir (in the conditional), se pouvoir (in the present)

   She may/might arrive at noon.
Elle arrivera peut-être à midi, Elle pourrait arriver à midi, Il se peut qu'elle arrive à midi.

Must = devoir (present tense)

   I must leave.
Je dois partir.
You must help me.
Vous devez m'aider.

Shall/will =  French future tense

   I shall/will help you.
Je vous aiderai.
He will arrive at noon.
Il arrivera à midi.

Should/ought to = devoir (in the conditional)

   I should/ought to leave soon.
Je devrais partir bientôt.
You should/ought to help me.
Vous devriez m'aider.

would (in the present) =  French conditional mood

   We would like to leave.
Nous voudrions partir.
I would help you if I were ready.
Je vous aiderais si j'étais prêt.

would (in the past) =  French imperfect tense

   He would always read when he was alone.
Il lisait toujours quand il était seul.
Last year, I would sleep until noon every day.
L'année dernière, je dormais jusqu'à midi tous les jours.
English modals may be followed by "have" plus a past participle to express perfect (completed) actions. Translating this construction usually requires a French verb in a perfect tense/mood followed by an infinitive.

could have =  pouvoir (in the conditional perfect)

   I could have helped you.
J'aurais pu vous aider.
We could have eaten.
Nous aurions pu manger.

may/might have =  peut-être, se pouvoir (plus past subjunctive)

   I may/might have done it.
Je l'ai peut-être fait, Il se peut que je l'aie fait.

must have =  devoir (in the passé composé)

  You must have seen it.
Vous avez dû le voir.
He must have eaten.
Il a dû manger.

Shall/will have =  French future perfect

  I shall/will have eaten.
J'aurai mangé.
He will have arrived by noon.
Il sera arrivé avant midi.

Should have = devoir (in the conditional perfect)

   You should have helped.
Vous auriez dû aider.
We should have eaten.
Nous aurions dû manger.

Would have =  French conditional perfect

   I would have helped you.
Je vous aurais aidé.
He would have eaten it.
Il l'aurait mangé.