It's mostly plastic, but they are incredibly robust. Back when I used a garden hose, I plumbed mine with metal turn spigots by using a reducing rubber sleeve over the output that was locked down onto the metal spigot. Eventually I gave up on the garden hose in favor of the improved flow rate of a 2 inch drainage line.
I wish I knew a little more about those totes. I lived in NW Arkansas a while, and they were abundant. You could get them used on Craigslist for about $50 reliably, sometimes better. And they were plentiful enough that you'd see people do things with them like cut the top all the way off and toss their trash in them by the curb for pickup.
Here in Michigan, I almost never see them. You definitely can't count on being able to find one when you want one. It's a shame, too, because they're 225 gallons, right? Almost five times as much volume as the 55 gallon barrel that most of us use for catching rainwater. Five times more storage for just a slightly larger footprint.
Can't .... do .... plaid .... So I did this tiny ad instead: