Due to their susceptibility to rust, steel storage units should be avoided. Among metal storage units, rust-free aluminum is usually the most sensible choice in siding. Metal siding is hardly the most visually appealing choice.
Organize For the Season - Now that you know what's staying in your shed, you must consider when you use the items. You don't want to move a stack of gardening tools just to get to the snow shovels you'll need in the winter. If possible, dedicate one side of the shed to warm-weather specific equipment and the other to cold-weather equipment. This will alleviate any confusion on where items are and save yourself plenty of time when working.