Les modaux en anglais servent à exprimer différents degrés de probabilité : must pour la quasi-certitude, may ou might pour une possibilité, et can't pour l'impossibilité.

Forte probabilité (je suis presque sûr)

MUST (= « ça doit se passer »)

Présent

must + base verbale

Exemple

He must be out. His car is not in the garage.

must + be + Ving

Exemple

She must be sleeping, she is not answering the phone.

Passé

must + have + participe passé

Exemple

He must have left. His car is not in the garage.

Futur

will + probably + base verbale

Exemple

She will probably leave early.

be + likely to + base verbale

Exemple

She is likely to leave early.

Probabilité plus faible

MAY (= « il se peut que »)

Présent

may + base verbale

Exemple

He may be back but I'm not sure.

may + be + Ving

Exemple

He may be waiting outside, let's look.

Passé

may + have + participe passé

Exemple

He may have left early but I'm not sure.

Futur

may + base verbale

Exemple

It may rain this evening.

Incertitude

MIGHT (= « il se pourrait que »)

Présent

might + base verbale

Exemple

She might be ill but she was fine yesterday.

might + be + Ving

Exemple

She might be having lunch out, she is not here.

Passé

might + have + participe passé

Exemple

They might have left already, I can't see them.

Futur

might + base verbale

Exemple

I heard it might snow tonight but I don't think so. It's too warm.

Impossible

CAN'T (= « c'est impossible »)

Présent

can't + base verbale

Exemple

She can't be British. She doesn't speak English.

can't + be + Ving

Exemple

They can't be going away, they have to work.

Passé

can't + have + participe passé

Exemple

She can't have phoned me. She hasn't got my number.

EN RÉSUMÉ