In the old days we used to keep opened tins in the fridge. I think
you could even buy a plastic lid to fit on the tin. Now we are told
to transfer the contents to another container.

Has the construction of tins changed, or is this another example of
excess caution? I have never known a tin to start rusting in the
timescale involved and even if it did, the rust would be at the top
not were the food is.