Contrastive Conjunction and Modal Perfect

How do you think about capital? Sorry I do not mean capital stock of money but modals in the past form. Know you of modals in English lessons? Well now we are going to learn about?

Modals in the past form are used in the past time.They are could, would, should, and might. Formula of modals is:
Modals + verb 1 + O/C.
Can be used in every tenses.
a.    Could is the past tense of can
The modal auxiliary could is used.
To express an ability in the past:
 -  I could always beat you at tennis when we were kids.
To express past or future permission:
  - Could i bury my cat in your back yard?
To express present possibility:
We could always spend the afternoon just sitting around talking.
b.    Would is the past tense of will
     The modal auxiliary would is  used to express a reapeated action in the past. When would is used in the past, it means “used to”, for example:
When i was younger, I would run two hours every day.
This means that I used to run two hours every day and now i don`t.  to express more polite  (request).
 Would you (please) feed the dog?
When would is used in the present, it show more polite. For unreal condition
-Mary would go to the Caribbean, but she doesn`t have enough money.(present)
- Mary would have gone to the Carribbean, but she didn`t have money.(past tense). Would, can is used in the past and present.
c.    Might is the past tense of may.
-Is used  to express of granting or seeking permission.
    Might, I leave class early?
-To express future possibility.
    She might be my advisor next semester.
-To express past possibility.
   Desty came late this morning, she might have missed the bus.
-  Might is considerably more tentative than may
d.    Should is the past tense of shall.
-Most commonly used to make recommendations or give advice. It can also be used to express obligation as well as ecpectation.
Example:
-When you go to Berlin, you should visit the palaces in Postdam. (recommendation)
-You should focus more on your family and less