Indeed I am not so caught up in my answer as not to see the other side of the story. 

I just tried to answer Tiago question, and make him see the point of the example he brought to the table.

I agree that most of the time "can" is the preffered form, that doesn´t make "may" unnatural in any way.  

I have recently read a novel of Grisham in which a little daughter talks to her father in this way, so it´s nothing far-fetched or unnatural.

I agreed with Swan, the example, and mhw, I just don´t rule out the "may" that can be used in certain given contexts.   No offense intended to anyone and please understand that I am not sticking to a point of view just because it´s "my baby", hee hee.