2 What are modal verbs?Modals (also called modal verbs, modal auxiliary verbs, modal auxiliaries) are special verbs which are different from normal verbs like "work, play, visit...“They give additional information about the function of the main verb that follows it.
3 Use of modal verbs: Express functions such as: Permission Ability ObligationProhibitionLack of necessityAdvicepossibilityprobability
4 Modal verbs are followed by an infinitive without "to“: Examples:You must stop when the traffic lights turn red.You look awful! You should see a doctor.Exception:You ought to go to the doctor.
5 must must not can could may might Modal VerbMeaningExpressingExamplemustto have to100 % obligationI must stop when the traffic lights turn red.to be very probablelogical conclusion (deduction)He must be very tired after such enormous workmust notnot to be allowed toprohibitionYou must not smoke in the hospital.canto be able toabilityI can swimto be allowed topermissionCan I use your phone please?it is possiblepossibilitySmoking can cause cancer !couldability in the pastWhen I was younger I could stay up all night and not get tired..more polite permissionExcuse me, could I just say something?It could rain tomorrow!mayMay I use your phone please?it is possible, probablepossibility, probabilityIt may rain tomorrow!mightMight I use your phone please?weak possibility, probabilityI might come and visit you in America next year, if I can save enough money.
6 need need not should/ought to had better Modal VerbMeaningExpressingExampleneednecessarynecessityNeed I say more?need notnot necessarylack of necessity/absence of obligationI need not buy any tomatoes. There are plenty in the fridge.should/ought toused to say or ask what is the correct or best thing to do50 % obligationI should / ought to see a doctor. I have a terrible headache.to suggest an action or to show that it is necessaryadviceYou should / ought to revise your lessonsto be very probablelogical conclusion (deduction)He should / ought to be very tired after such enormous workhad betterYou 'd better revise your lessons
7 GOLDEN RULES ABOUT MODAL VERBS Modal verbs never add an -s in the third person singular: He must work harder to pass his examsModal verbs don’t need auxiliaries to make negative sentences or questions: Should I apologise?I mustn´t smoke in hospitalsModal verbs only have one form. You need other verbs to express the same thing in the past, future etc.I´ve been able to finish on time.
8 EXPRESSING ADVICEWe use should and ought to to express advice or make recommendations: You should eat less fat if you want to lose weight.You ought to relax if you don´t want to get ill.You shouldn´t be rude to anybody.You oughtn´t to tell lies.
9 EXPRESSING OBLIGATION OR NO OBLIGATION We use must and have to to express obligation.The difference between them is: We use must when the obligation is inside the speaker. It is a moral obligation.We use have to when the obligation is outside the speaker. It comes from the situation.
10 EXPRESSING OBLIGATION OR NO OBLIGATION I must do some exercise to get fit.We have to be quiet in class. That’s the rule.Note: Have to is not a modal verb. We use don’t / doesn’t have to, needn’t and don’t /doesn’t need to to express no obligation.You don’t need to get up early. It is Sunday!She doesn’t need to wear a coat. It is warm outside.She needn’t cook tonight. We´re eating out.
11 EXPRESSING PROHIBITION We use mustn’t to express prohibition.Children under 16 mustn’t go in there. At school we mustn’t smoke.