Trouble about solid, beam, trusses, sheet metal

hi, I wanna ask, why is my fea result is different if I define my part as solid or beam. isn't it supposed to be the same? What makes both got different result? Could you someone tell me more about the condition when to use sheet, truss ,beam or solid. In my opinion, I thought that to get accurate result, Solid type must be used as it represent the exact shape of the part. Please need advice on this matter, still confusing me and very hard for me to decide what to choose.

SolidworksSimulation