Modal verbs Can and Could

In general, modal verbs syntax is the same for all:

Affirmative
Subject + [can/could+ verb(simple form)] + Complement

Negative sentences
Subject + [can't/couldn't+ verb(simple form)] + Complement

Question form
Question word + [Can/Could + verb (simple form)] + Complement
USE

A) Ability ( Can : present , Could : past )

To express an ability we use can/could
- Sheila can play the guitar very well
- When I was a child I could play all day.
- Greg can't cook at all.
- Can you speak French?
- Pete could sing when he was in college.

Note:
Remember that when you talk about ability, can is used for present and could or past abilities

B)Possibility: (Can = Could)
When you express possibility can = could.
- I think it (can/could) rain.
- I (can/could) buy a new car because I have a good job.

C) Other uses:

• Can - to ask permission: Can I go to the Bathroom? (May : formal)
• Can / Could you bring me some Coffee? : Ask Favor (Pedir favores)

Nota: Tengan cuidado con traducir el can y could. Esto no ayudara pues como ven, dependiendo del uso, can puede ser igual a could o distinto. No basta decir que can es puedo y could podría. Recordar los usos y serán exitosos. Hagan esto en general pero especialmente con los modal verbs. Aprendan el uso siempre y después si quieren lo interpretan en español.