[Grammar] How can/may I help you?

[NAL123]

Consider this sentence of mine, please:

How can/may I help you?

Do can and may here mean possibility or they mean permissibility?

Can I replace can/may with could/might?

 

[emsr2d2]

How can I help you? (Normal, everyday acceptable usage.)
How may I help you? (Formal, normal, acceptable usage.)
How might I help you? (Grammatically correct but old-fashioned.)

How could I help you? (Grammatically correct but doesn't mean the same as the others.)

 

[NAL123]

How could I help you? (Grammatically correct but doesn't mean the same as the others.)

How is "How could I help you" different than the others?