What do you call the metal pieces that hold a truss together?

The metal pieces that hold a truss together are commonly referred to as connectors or truss connectors. These connectors can include various types of fasteners, such as bolts, plates, and brackets, designed to join the individual members of the truss securely. In some contexts, they may also be called gusset plates, especially when they are flat metal plates used to connect the joints of a truss.