Is it gramatically corect to say "May you help me?". I know you can say "Will you help me?" and it is not gramatically correct "Can you help me?". Thank you for all your help.
I'd say that may is often used with the first person sg.
In studies of spoken English, The Longman Grammar of Spoken and Written English found that "[D]espite a well-known prescription favoring may rather than can for expressing permission, may is especially rare in the sense of permission. ... many of the instances of may marking permission ... are produced by caregivers in conversations with children."
[LGSWE page 493]