This chapter discusses the types of sensors used in sheet forming operations and the information they provide. It explains how force sensors protect equipment from overloads due to tool wear, friction, and misfeeds, how displacement and proximity sensors help to prevent die crashes, how acoustic emission, ultrasonic, and eddy current sensors detect tool breakage and part defects such as cracks, and how roller ball and optical sensors measure material flow. It also discusses the role of draw-in, wrinkle, oil-monitoring, and vision sensors and explains how material properties can be derived in real time from various sensor outputs.