Replacing old light fixture- is the silver postive or is the br? Or doesn't it matter?

I just pulled down a old light fixture to replace it. The box has 2 blk 2 wht and a ground, the current fixture only used the white wires, one was connected to what looks like a silver screw and one to what appears to be a br screw. All the fixtures I've installed before wire blk to blk and wht to wht. Do I do this one the same? Or is there something different going on?