As far as I know, there are no major bugs in the first level, so it's likely because when an object in this game is given a heavy property it can't be moved. To make the metal boxes move, you have to give the metal boxes the property of the wood box.
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Ya, so I got to a point where I could press E on the metal boxes and get through to where the wood boxes are, but it wasn't very clear when I was holding a crate or not. Like, E showed up, I press E, and sometimes the box would move a little, so I tried holding E. How exactly does moving crates work, it was really hard to tell if I was in a move state or not