Se você poder corrigir meu português. Eu só sou aprendo I COULD walk to the house. - In isto caso significa que eu posso, talvez eu vou ir, talvez eu não vou ir I CAN walk to the house - In isto caso significa que eu posso. Não mais. I SHOULD walk to the house - In isto caso significa que eu penso que é boa ideia andar I MAY walk to the house - In isto caso significa talvez eu vou ir, talvez eu não vou ir. Isso ou um pessoa me permiti andar

Correction: When can I use the words "can," "could," "should," and "may?" CAN: "less formal / less polite than COULD" >> Can I borrow your phone? -(Request / Informal)- >> Can I join you? -(Asking for permission / Informal)- >> Sure! You can sit next to me. -(Giving permission / Informal)- >> That small dog can be very aggressive when threatened. -(Possibility / Something that may happen at a future time.)- >> Can I help you? -(Offering something to someone)- >> I can dance. -(Present ability)- COULD: "more formal / more polite than CAN" >> Dad, could you please help me with my homework? -(Request / More polite)- >> Could I take the entire afternoon off? -(Asking for permission / More polite)- >> I could have been the class president, but I quit during the campaign. -(Assumed possibility, somewhere in the past, that didn't happen.)- >> You could order this dish next time. -(Suggestion)- >> Mary could speak French and Spanish when she was in elementary school. -(Past ability)- MAY: "more formal / more polite than COULD" >> May I borrow your pen? -(Request / Formal)- >> May I sit beside you? -(Asking for permission / Formal)- >> You may eat some snacks during our class. -(Giving permission / Allowing something / Formal)- >> It may rain this afternoon. -(Possibility)- >> You may not enter the a private hunting ground for any reason without obtaining a permit from the Mayor's office. -(Prohibition)- >> May you have many more birthdays to come. -(Wish for someone)- SHOULD: "weaker than MUST" >> You should be here before the start of the party. -(Obligation to someone)- >> You should eat more veggies. -(Friendly Advice / Suggestion)- >> Low-end smartphones in the Philippines shouldn't cost you more than a hundred dollars. -(Expectation about something)- :-)

"can" and "may" are sometimes used in the wrong context. For example: if you are in class and you need to go to the toilet, then you should ask your teacher: "May I go to the toilet please?" But quite often people would say: "Can I go to the toilet please?" The teacher might respond to the last question with: "I am not sure, can you?" because the use of "can" here refers to the question whether you are actually physically able to go or not. Not that you are asking permission to do so.

Could - at past time Can - at present time May-at present time. May I go out? Should - wen u recommend smth, give advices. You should learn English. You should stay here.