The way they used to be.
Harder core than you. Harder than anything.
Plastic milk crates may seem indestructable, but metal ones, well, from what I can tell, they are indestructable.
And they have all those sharp metal edges, too! Surprise
The metal construction is, in fact, the only significant flaw in the design of these crates, from the perspective of the non-milk-transporting user - they scratch up wood surfaces. Easily. Fast. They are a bit heavier than plastic milk crates, too, but they are metal!
Otherwise, they are identical in form factor to plastic milk crates - designed to hold four 1 gallon containers of milk - and they are completely compatible with plastic crates.
Metal milk crates were replaced by plastic ones due to lower production costs.
You know you want them.