Metal nanocrystals support unique light-matter interactions through a phenomenon known as the localized surface plasmon resonance (LSPR). These resonances show a great deal of sensitivity to their local environment, and by altering this environment it is possible to produce new, "hybridized" plasmon modes. The far-field spectral qualities, and the near-field electromagnetic properties can by heavily manipulated through the generation of hybridized plasmon modes. This work explores the properties and functions of hybridized plasmon modes in a variety of systems. Finite-difference time-domain modelling use used to correlate the experimental spectral response is with the calculated near-field spatial distribution of hybridized modes in a number of systems involving silver nanocubes (AgNC). These systems demonstrate it is possible to carefully monitor the environment of a nanocrystal, induce an unusually sharp spectral extinction in dielectric-coated AgNCs, and manipulate the spatial distribution of plasmon modes in colloidal composite Ag@Cu2O core-shell nanocrystals. These properties are applied to functional materials, including photothermal and colour patterning of a plasmonic system driven by the embedment of an AgNC into a polymer matrix. The spectral signature of hybridized plasmon modes is used to both characterize and manipulate the degree of photothermal heating in this thermoplasmonic patterning system. Hybridized gap-plasmons are used to generate wide range of colours, with controllable palettes using AgNC-over-Au and AgNC-over-Ag nanoparticle-over-mirror (NPoM) films. Lastly the potential for alternative plasmonic materials for ultraviolet (UV) plasmonics was explored. The potential for In and Al nanocrystals for UV surface-enhanced Raman spectroscopy was investigated. All these systems demonstrate the potential and advantage of using hybridized plasmon modes to manipulate the far-field and near-field optical response of functional plasmonic materials.