Ability –Possibility- probability-permission-advisability-necessity-requesting-assistance-making –conclusions-giving instructions-making suggestions-showing preference-making offers-maing promises or predictions Function | MODAL(S) | ability | can -could | possibility | could -may -might | probability | must -must not | permission | may -can -could | advisability | had better-ought to-should | necessity | have got to -have to -must | lack of necessity and prohibition | do not have to -must not | requesting assistance | can -could -will -would | making conclusions | must | giving instructions | simple form of a verb | making suggestions | let's -why don't | showing preference | like ... better than ... -prefer -would rather | Modal | Function(s) | can | ability -permission -requesting assistance | could | ability -requesting assistance | had better | advisability | have to | necessity | have got to | necessity | let's | making suggestions | like ... better than ... | showing preference | may | possibility -permission | might | possibility | must | probability -necessity -making conclusions | must not | prohibition | prefer | showing preference | simple form of the verb | giving instructions | why don't | making suggestions | will | requesting assistance | would | requesting assistance |

Modal | Nature | Contraire | Exemples | be able to | possibilité | cannot ou be unable to | I was able to prevent the theft but I was unable to arrest the thief. | can | possibilité, capacité | cannot | Birds can fly; monkeys cannot. | | permission | cannot ou may not | Can I watch TV? No, you can't. | could | possibilité, capactié | could not | Could there be a virus in this file? No, there couldn't; I ran the anti-virus. | | possibilité (passé) | could not | Could dodo birds fly? No, they couldn't. | | permission | cannot ou may not | Could I open the window? No, you may not. | had better | conseil |