Modal verbs are special verbs which behave very irregularly in English. They are very common and thus you should pay attention to them.
Here are some important differences:
1. Modal verbs do not take "-s" in the third person.
He can speak English fluently.
Mike should be here by now. I wonder what's going on. He's always on time.
2. You use "not" to make modal verbs negative, even in Simple Present and Simple Past.
She should not (shouldn't) leave without asking her boss.
They may not go on holiday this year.
3. Many modal verbs cannot be used in the past tenses or the future tenses.
will can come with us. It is Not Correct.
musted study very hard. It is Not Correct.
You should you an equivalent instead:
CAN = BE ABLE TO
He will be able to come with us.
MUST = TO HAVE TO
You had to study very hard.
4. Modal verbs have no infinitives or participles. Instead we use other expressions like " be able to, be allowed to, have to".
He is not allowed to tell you this.
I will not (won't) be able to come to work tomorrow.
Here are the most common Modal Verbs and their uses:
|CAN||1. ABILITY/POSSIBILITY||They can speak English fluently.|
|CAN||2. INABILITY/IMPOSSIBILITY||I can't repair my car alone.|
|CAN||3. ASKING FOR PERMISSION||Can we smoke in this room?|
|CAN||4. REQUEST||Can you help me?|
|COULD||1. ASKING FOR PERMISSION||Could I borrow your dictionary?|
|COULD||2. REQUEST||Could you say it again more slowly please?|
|COULD||3. SUGGESTION||Mike could try to find a better job.|
|COULD||4. FUTURE POSSIBILITY||I think they could have another crisis.|
|COULD||5. ABILITY IN THE PAST||She gave up her job so she could take a gap year.|
|MAY||1. ASKING FOR PERMISSION||May I have another cup of tea?|
|MAY||2. FUTURE POSSIBILITY||India may become a major economic power.|
|MIGHT||1. PRESENT POSSIBILITY||We'd better phone them later, they might be watching a film.|
|MIGHT||2. FUTURE POSSIBILITY||The shop might give us a 10% discount.|
|MUST||1. PROHIBITION||They mustn't enter the room.|
|MUST||2. NECESSITY / OBLIGATION||We must go now, it's getting late.|
|SHOULD||1. SAYING WHAT'S RIGHT OR WRONG||I should sort out this problem at once.|
|SHOULD||2. RECOMMENDING ACTION||I think we should check everything again.|
|SHOULD||3. UNCERTAIN PREDICTION||Prices should go up again next year.|
|WILL||1. INSTANT DECISIONS||I can't see any buses so I'll walk home.|
|WILL||2. OFFER||I'll make you a nice cup of tea.|
|WILL||3. PROMISE||I'll phone you first thing in the morning.|
|WILL||4. CERTAIN PREDICTION||The price of oil will increase again.|
|WOULD||1. ASKING FOR PERMISSION||Would you mind If I came a bit later?|
|WOULD||2. REQUEST||Would you pass me the salt please?|
|WOULD||3. MAKING ARRANGEMENTS||Would 3.30. suit you?|
|WOULD||4. INVITATION||Would you like to play golf next Saturday?|
|WOULD||5. PREFERENCES||Would you prefer tea or coffee?|
|SHALL||1. OFFER||Shall I help you with your luggage?|
|SHALL||2. SUGGESTION||Shall we say 3 o'clock then?|
|SHALL||3. ASKING WHAT TO DO||Shall I answer the phone for you?|
|OUGHT TO||1. SAYING WHAT'S RIGHT OR WRONG||We ought to buy a new car.|
If you want to know more about MODAL VERBS in general, just click HERE.