Which is Better? Can or May?

When I was in grade school I had a teacher who would always correct us whenever we would ask, "Can I go to the bathroom?"  She would continually remind us, "May I go to the Bathroom?"  What's the difference?  Can means am I capable, while may requests permission.  As kids we would laugh about it, but the lesson stuck.  This lesson was just a small part of the reading comprehension I would learn, and also that words matter.  My reading comprehension skills would serve me well, first when I took civil service tests and then when I became a law enforcement officer.  Any Law Enforcement Officer knows that it is of utmost importance to understand and differentiate words like: may, must, should, shall, and even 'and' and or.

The new Ford commercials humorously drive home the point.  Watch, learn and enjoy.