A family of modules called global Weyl modules has recently been defined over generalized loop algebras. Part I of this dissertation contains a characterization the homomorphisms between these global Weyl modules, under certain restrictions. The crucial tool in this section is the reconstruction of the fundamental global Weyl module from a local one. In Part II, global Weyl modules are defined for loop algebras which have been twisted by a graph automorphism of the Dynkin diagram. We analyze their relationship with the twisted local Weyl module and with the the untwisted global Weyl module.