A trim is used for being covered on a vertical beam of a shelving system, wherein the trim is matched with the shape of the vertical beam, and the trim is configured such that when the trim is covered on the vertical beam, a force is generated between the trim and the vertical beam, the trim is fixed on the vertical beam with the force and the trim is covered on at least part of the surface of the vertical beam. A vertical beam assembly comprises a vertical beam and a trim which is covered on the vertical beam. A shelving system comprises a horizontal beam and a vertical beam which contains a magnetic trim. The connection mode between the trim and the vertical beam is very convenient for installation and disassembly. The trim is covered on the vertical beam, which may improve the overall aesthetics of the vertical beam and prevent other items from being hooked on the vertical beam and thus causing damage to the shelving system.