It is very important to know which verbs are normal and which are special, because the sentence structure is different in each case.

SPECIAL VERBS

They can do everything, they never need help. Special verbs are auxiliaries and modals, and there are only 13:

auxiliaries: to be, have, do
modals: can/could, will/would, shall/should, may/might, must, ought to

NORMAL VERBS

All the other verbs are normal. They can only build an affirmative sentence. For all the other constructions they need to use DO (DOES for the 3rd person singular in the simple present, DID for the past)

Special verbs follow the rule of the three NO's: No -S, No To, No Do

SPECIAL VERBS			compare:	NORMAL VERBS
NO –S		I can / she can		I want / She wants
NO TO		I can walk / to can		I want to go / to want
NO DO		you can / you can’t / can you?		you want / you don't want / do you want?

❶- No S: Special verbs don't add an -S for the third person singular in the simple present tense. The forms is, has are irregular forms, but still, they are not bes (be + S) or haves (have + S)

❷- No To: Special verbs are never followed by an "infinitive with to" (exception: ought to), and they don't have an infinitive form (exception: to be). To do and To have are different from Do and Have. Compare:

- Do = special (auxiliary verb, no meaning):     Do you like it?
- To Do = normal verb:     I do yoga in the mornings / Do you do yoga?
- Have = special (auxiliary verb, no meaning):     Have you ever been to London?
- To Have = normal verb:     I have a car / do you have a car?
Note: Have got = have (special) + got (normal):     Have you got a car?

❸- No Do: Special verbs never use DO

I can't speak Russian (not: I don't can speak Russian)
Are you Polish? (not: Do you are Polish?)

Abbriviations used here:  s.v.= special verb  n.v.= normal verb  S= subject  V= verb  O= object, adverbial, complement

Let's see how these three rules work in practice, shaping the 4 most common constructions in the language

AFFIRMATIVE  

s.v. & n.v.   S+V+(O)

- I am Spanish
- He can speak English

- You live in London
- She likes Japanese music

NEGATIVE

s.v.   S+ V+not  +(O)
- I am not French
- She can’t speak Italian

n.v.   S+do+not +V+(O)
- You don’t live in Rome
- She doesn’t like Jazz

QUESTIONS

s.v.   V+S +(O) ?
- Are you Spanish?
- Can she speak English?

n.v.   do+S +V+(O) ?
- Do you live in London?
- Does she like Japanese music?

SHORT ANSWERS

s.v.
Are you Spanish?  Yes, I am / No, I'm not
Can she speak English? / Yes, he can / No, he can't
n.v. (use do)
Do you live in London?  Yes, I do / No, I don't
Does she like Japanese music?  Yes, she does / No, she doesn't

(simple rule: for Short Answers, the same verb that starts the question is the verb that will finish the answer)