I know that the following sentence is correct:
If it rains, I will stay at home.
My question is if the following sentence is also correct when you are not so sure about what you are going to do:
If it rains, I would stay at home.
I've seen 'It wouldn't surprise me if it were true.' Above sentence is using "would" instead of "will". Is this a very special case? Or it is natural and means we can use "would" instead of "will" when we are not so sure?
Thank you in advance!