Comunication

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.
Examples:
* 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.
Examples:
* He should not be late.
* Theymight not come to the party.
3. Many modal verbs cannot be used in the past tenses or the future tenses.
Examples:
* He will can go with us. Not Correct
* She musted study very hard. Not Correct
In this lesson, 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 ofteninterchanged with them.
All the auxiliary verbs except be, do and have are called modals. Unlike other auxiliary verbs modals only exist in their helping form; they cannot act alone as the main verb in a sentence.
Be, do, and have also differ from the other auxiliaries in that they can also serve as ordinary verbs in a given sentence.
The modal verbs are:-CAN / COULD / MAY / MIGHT / MUST / SHALL / SHOULD / OUGHT TO /WILL / WOULD 
!Note The modal auxiliary verbs are always followed by the base form.

Can
"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.
Examples:
I can ride a horse. ability
We can stay with my brother when we are in Paris. opportunityShe cannot stay out after 10 PM. permission
Can you hand me the stapler? request
Any child can grow up to be president. Possibility
Could
"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."
Examples:
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
May
"May" is most commonly used to express possibility. It can also be used to give or request permission, although this usage is becoming lesscommon.
Examples:
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
"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 isless common in American English.
Examples:
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
"Must" is most commonly used to express certainty. It can also be used to express necessity or strong recommendation, although nativespeakers 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.
Examples:
This must be the right address! certainty
Students must pass an entrance examination to study at this school. necessity
You must take some medicinefor that cough. strong recommendation
Jenny, you must not play in the street! Prohibition
Ought To
"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...