The materials for nanoplasmonics include metals, in particular, alkaline, alkaline earth and transition metals (including noble metals such as silver, gold and platinum), semi-metals such as graphene, semiconductors (highly doped semiconductors used as plasmonic metals or lightly doped semiconductors used as gain media), topological insulators (whose surfaces can exhibit plasmonic properties) and dielectrics. In Part 1 of this four-part tutorial, Mark Stockman deals with fundamental properties of the materials. Among those, he concentrates on dispersion properties of the plasmonic materials defined by the fundamental principle of causality. The tutorial also compares metals with conducting semiconductors and graphene. Novel two-dimensional semiconductors such as transitional metal dichalcogenides are also discussed.