This would always be a perfect opportunity for me to teach the class the difference between “can”, “may” and “will” (I love to use teachable moments – pupils remember them better when they have a real-life context to use!). The use of the modals (the 3 words are called modals, from the root word with the same meaning as “modify”) changes the meaning of the verbs following and must be used with care.
“Can” is used to indicate the ability to do something. I can walk away from my seat without crutches, but someone who’s injured cannot – he does not have the ability to do so without his clutches.
“May” is used to indicate permission most of the time. So while I can walk away from my seat without clutches since I’m perfectly healthy, I may not do so because my teacher does not give me the permission. So I guess I can only squirm (a common thing happening to this suspected-dyslexic-and-ADHD case back when I was a pupil).
“Will” is used to indicate a high certainty or even a certainty. So I can walk away from my seat because I am perfectly healthy, but I may not because my teacher does not give me the permission. And I most certainly will not because I don’t want to get into trouble with my teacher (I might have been the class clown, but I was no discipline case)!
Next time you say something, be careful of the modal you use!