Kind Of Modal

1. Can
Function
a. Present ability
    example : she can make a cake
                   he can do his homework
b. Asking permission
    example : can i visit you?
c. Giving permission
    example : you can use my bicycle
d. Offering
    example : can i help you to take coffee ?
e. Possibility
    example : you can be richman if you work hard

2. Could
Function
a. Past ability
    example : when my mother was still young, he could sing beautifully
b. Asking permission
    example : could i borrow your book ?
c. Possibility
    example : she could be at home now, bit she usually plays volley ball.

3. Shall
Function
a. Expressing plan
    example : i shall go to london
b. Offering
    example : shall i make coffee for you ?
c. appointment
    example : you shall have motorcycle