1
When I visit you next year, I will can speak English better.
When I visit you next year, I will be able to speak English better.
I’d like to can play the guitar.
I’d like to be able to play the guitar.
I haven’t could contact you before.
I haven’t been able to contact you before.
Can and could do not have all the forms that other verbs have. Use the correct form of be able to after another modal verb (will, may, might, must, etc.), after to, in perfect tenses and in -ing forms: ‘She might be able to help.’ ‘I have never been able to swim.’ ‘I like being able to work from home.’
2
There can be a strike next week.
There may/might be a strike next week.
When you are not sure whether a particular future event will happen, use may or might, not can.
3
‘Where are my glasses?’ ‘They can be on your desk.’
‘Where are my glasses?’ ‘They could/may/might be on your desk.’
In a positive sentence about one uncertain possibility now, use could, may or might. Use can for things that are generally possible: ‘This road can be dangerous in winter.’
See MUST (2)