I use 5 gallon buckets under the counter that holds my cutoff saw. I use a bucket for solid steel, one for aluminum tube, one for steel tube, one for flat chunks, one for little bits. I worked in a shop where the buckets were held on an angle in the space between the counter and the shop wall (there was lots of space due to the structural steel holding the building up, the counter couldn't be snug to the wall.) This was super convenient, the angled buckets cause all the long pieces to settle neatly in the bucket, and you could see into the buckets.
I built a rack for the wall above my cutoff saw for longer pieces. I used scavenged telestrut (square tube with holes in it) for the verticals and welded up shelf brackets from angle. I don't use shelves, so it's easier to see what is in the rack from below.
I also store long flat stock and some offcuts behind the fence but on my counter top by the cutoff saw. This is sub-optimal, but easy. Counter is 2 ft deep, but saw is set to use middle 9 inches which leaves room behind the fence, and along the front edge to stack pieces as they are cut. I used a 1x3 on flat as a fence on the left (feed in) side of the saw, and nothing as a fence on the right. I screw a stop block to the counter if needed.
First pic shows the rack on the far left. Then some more pix of the rack, you can see the buckets under the counter. I use the inside of the shelf brackets for small stuff like threaded rod, pencil rod, etc.
The 2nd to last pic shows the saw set in the middle of the counter.
The 3rd pic has my homemade stock support clamped in the cutoff saw vise. When I need to cut wood or aluminum, I set my chopsaw on the counter, and set the supports on it too. That's what the last pic shows.
BTW, the pix are from when I moved into that shop and it has NEVER been that uncluttered again

And, yeah, I know that counter is rough. I banged it together quickly from existing pieces 15 years and 2 shops ago. It got the job done and earned me plenty of money! I have a tendency to do "just enough" when I'm busy working, and then I live with the 'temporary' result for years.
Zuk