Can/could

We use can/could with the basic verb (without "to").

√ I/you/he/she/it/we/you/they can/could walk...
X I/you/he/she/it/we/you/they can’t/couldn’t play...
? Can/Could I/you/he/she/it/we/you/they find...

Can is used for present time e.g. I can sing quite well.
OR
for future time e.g. I can drive you to work tomorrow.

Could is used for past time e.g. I couldn’t call you yesterday.

We use can/could for:
→Permission e.g. You can’t use your phone during an exam.
→Ability e.g. I can speak 3 languages.
→To ask for something e.g. Can I have a glass of water, please?
→To offer help e.g. Can I help you carry your shopping bags?