How safe would it be to leave food in opened cans?

I can remember in past days that doing so would cause lead poisoning.
I am not sure what they line the cans with now, but I am sure it does
not contain lead.

How safe would it be to open a can of beans and eat half and put the
other half covered in the fridge? Leave it for a day? Leave it for a
week?

I don't like to wash dishes.