Some lengths of plastic Rainwater Guttering (or similar) can make an easy to use Metal Store. Put them on a wall that you can't use for anything else, maybe behind a door. They don't stick out far. Use plenty of brackets to take the weight.
No more rummaging round in boxes or under the bench for that bit of metal you knew you had somewhere!
Easy to store your metal in and easy to find the right size when you want it.