Peptide nanomaterials via the molecular design and controllable self-assembly provide potential nanoscale building blocks for the synthesis of functional hybrid nanomaterials. Peptide can be hybridized with various nanomaterials, such as nanoparticles (NPs), quantum dots (QDs), nanowires, and two-dimensional (2D) materials (like graphene) through both covalent and noncovalent interactions. In this chapter, we carry out the case studies on the conjugation of self-assembled peptide nanomaterials with various metallic nanoparticles (MNPs), including gold, silver, and others. Meanwhile, the potential applications of the peptide/MNP hybrid nanomaterials for biosensors, bioimaging, drug deliver, and cancer therapy are presented and discussed.