This superior verite doc opens a wide window onto the world of scrap-metal scavengers, thousands of whom comb Chicago’s back alleys in battered pickups looking for recyclable metals. Theirs was a hard buck to earn even before metal prices plummeted in 2008 from $230 to $60 a ton, and directors Ben Kolak, Brian Ashby, and Courtney Prokopas make the most of their subjects’ humble heroism while resisting the temptation to sentimentalize them. Along the way they painlessly impart a whole lot of insight into the travails of undocumented immigrants, the persistence of segregation, and the workings of the globalized economy. Miraculously, the whole thing plays more like a gritty valentine to the City in a Garden than an earnest left-wing guilt trip.