Here is a grammar reference to modal verbs.
Modal Verb Tutorial
What are Modal Verbs?
Modal verbs are special verbs which behave very differently from normal verbs. Here are some important differences:
1. Modal verbs do not take “-s” in the third person.
* He can speak Chinese.
* She should be here by 9:00.
2. You use “not” to make modal verbs negative, even in Simple Present and Simple Past.
* He should not be late.
* They might not come to the party.
3. Many modal verbs cannot be used in the past tenses or the future tenses.
* He will can go with us. Not Correct
* She musted study very hard. Not Correct
Common Modal Verbs
Must Ought to
For the purposes of this tutorial, we have included some expressions which are not modal verbs including had better, have to, and have got to. These expressions are closely related to modals in meaning and are often interchanged with them.
# Had Better
# Have to
# Have Got to
# Ought to
“Can” is one of the most commonly used modal verbs in English. It can be used to express ability or opportunity, to request or offer permission, and to show possibility or impossibility.
* I can ride a horse. [ability]
* We can stay with my brother when we are in Paris. [opportunity]
* She cannot stay out after 10 PM. [permission]
* Can you hand me the stapler? [request]
* Any child can grow up to be president. [possibility]
“Could” is used to express possibility or past ability as well as to make suggestions and requests. “Could” is also commonly used in conditional sentences as the conditional form of “can.”
* Extreme rain could cause the river to flood the city. [possibility]
* Nancy could ski like a pro by the age of 11. [past ability]
* You could see a movie or go out to dinner. [suggestion]
* Could I use your computer to email my boss? [request]
* We could go on the trip if I didn’t have to work this weekend. [conditional]
“Had better” is most commonly used to make recommendations. It can also be used to express desperate hope as well as warn people.
* You had better take your umbrella with you today. [recommendation]
* That bus had better get here soon! [desperate hope]
* You had better watch the way you talk to me in the future! [warning]
“Have to” is used to express certainty, necessity, and obligation.
* This answer has to be correct. [certainty]
* The soup has to be stirred continuously to prevent burning. [necessity]
* They have to leave early. [obligation]
Have Got To
“Have got to” is used to express necessity and obligation.
* Drivers have got to get a license to drive a car in the US. [necessity]
* I have got to be at work by 8:30 AM. [obligation]
“May” is most commonly used to express possibility. It can also be used to give or request permission, although this usage is becoming less common.
* Cheryl may be at home, or perhaps at work. [possibility]
* Johnny, you may leave the table when you have finished your dinner. [give permission]
* May I use your bathroom? [request permission]
“Might” is most commonly used to express possibility. It is also often used in conditional sentences. English speakers can also use “might” to make suggestions or requests, although this is less common in American English.
* Your purse might be in the living room. [possibility]
* If I didn’t have to work, I might go with you. [conditional]
* You might visit the botanical gardens during your visit. [suggestion]
* Might I borrow your pen? [request]
“Must” is most commonly used to express certainty. It can also be used to express necessity or strong recommendation, although native speakers prefer the more flexible form “have to.” “Must not” can be used to prohibit actions, but this sounds very severe; speakers prefer to use softer modal verbs such as “should not” or “ought not” to dissuade rather than prohibit.
* This must be the right address! [certainty]
* Students must pass an entrance examination to study at this school. [necessity]
* You must take some medicine for that cough. [strong recommendation]
* Jenny, you must not play in the street! [prohibition]
“Ought to” is used to advise or make recommendations. “Ought to” also expresses assumption or expectation as well as strong probability, often with the idea that something is deserved. “Ought not” (without “to”) is used to advise against doing something, although Americans prefer the less formal forms “should not” or “had better not.”
* You ought to stop smoking. [recommendation]
* Jim ought to get the promotion. [It is expected because he deserves it.]
* This stock ought to increase in value. [Probability]
* Mark ought not drink so much. [advice against something ](notice there is no “to”)
“Shall” is used to indicate future action. It is most commonly used in sentences with “I” or “we,” and is often found in suggestions, such as “Shall we go?” “Shall” is also frequently used in promises or voluntary actions. In formal English, the use of “shall” to describe future events often expresses inevitability or predestination. “Shall” is much more commonly heard in British English than in American English; Americans prefer to use other forms, although they do sometimes use “shall” in suggestions or formalized language.
* Shall I help you? [suggestion]
* I shall never forget where I came from. [promise]
* He shall become our next king. [predestination]
* I’m afraid Mr. Smith shall become our new director. [inevitability]
“Should” is most commonly used to make recommendations or give advice. It can also be used to express obligation as well as expectation.
* When you go to Berlin, you should visit the palaces in Potsdam. [recommendation]
* You should focus more on your family and less on work. [Advice]
* I really should be in the office by 7:00 AM. [obligation]
* By now, they should already be in Dubai. [expectation]
“Will” is used with promises or voluntary actions that take place in the future. “Will” can also be used to make predictions about the future. For more information on using “will” and associated exercises, visit the Simple Future section of our Verb Tense Tutorial.
* I promise that I will write you every single day. [promise]
* I will make dinner tonight. [voluntary action]
* He thinks it will rain tomorrow. [prediction]
“Would” is most commonly used to create conditional verb forms. It also serves as the past form of the modal verb “will.” Additionally, “would” can indicate repetition in the past.
* If he were an actor, he would be in adventure movies. [conditional]
* I knew that she would be very successful in her career. [past of “will”]
* When they first met, they would always have picnics on the beach. [repetition]
Modal verbs in the past
When modal verbs point to the past, then “have” is used as an auxiliary + a past participle of the main verb.
* If he had been an actor, he could have acted in adventure movies. [conditional]
* It must have been Susan the person who phoned this morning. [certainty]
* I should have studied more. [regret]