Will can express insistence/willingness and won't refusal/unwillingness in the present.

"I'll go anyway!"
"You won't!"
"Yes, I will!"

"I won't do it!"
"Yes, you will!"

Couldn't can express unwillingness.

I couldn't lie to you.

Modals expressing past willingness / unwillingness
Willingness / unwillingness with modals Modals and their meaning

Login or register to access a printer-friendly version, add page to favourites or post a question in the forums.