Arrays of free-standing metallic nanorods are promising candidates for sensors, switches and spectroscopy. They have structure sizes much smaller than the wavelength of visible light, feature a long-axis surface plasmonic resonance (LSPR) and show metamaterial-like properties. This thesis provides a detailed investigation of their linear optical properties and highlights some nonlinear optical aspects.rnrnBy means of graded structures having a tunable LSPR and three different theoretical models -- a numerical multiple-multipole method (MMP) model, a semi-analytic collective surface plasmon (CSP) model and an analytic dipolar interaction model (DIM) -- the optical properties were analyzed. Using the DIM, the experimentally observed blueshift of the LSPR in comparison to a single nanorod is confirmed and a physical explanation is provided. The LSPR strongly depends on the angle of incidence and the rod diameter. However, for a varying length the changes are small with the long-axis mode showing a lower energy limit. The detailed arrangement of the nanorods and the azimuthal angle of the incoming light plays only a minor role for small nanorod separations. Similarly, the dependence on the metal is the same as for single particles, whereas the sensitivity to the surrounding dielectric is much stronger than in the single-particle case. rnFor longer nanorods made of silver, angle-dependent higher-order modes are observed and reproduced using MMP. The CSP model is applied and Fabry-Pérot-like oscillations of the CSPs are found. The propagating nature of these modes leads to the discovery that the p component of the transmitted light experiences a phase jump and to the observation of polarization conversion inside the structures.rnNegative refraction is found in nanorod arrays; it is revealed that a negative energy flux occurs only within a bandwidth given by the LSPR of a single nanorod and the array resonance. For smaller wavelengths, the in-plane component of the Poynting vector reverses, leading to an (extraordinary) positive flux. At the LSPR itself, the flux parallel to the surface is found to be zero. The negative refraction is also exploited to mimic a nanolens with structure parameters that are infact technical realizable. In the visible regime the nanolens shows a NA of 1.06 and superlens-like features such as identical rotation and linear translation of image and object.rnrnThe nonlinear measurements on graded structures are conducted using femtosecond pump-probe spectroscopy resulting in kinetics showing either an increased transmission or absorption with signal changes of up to 40%. By converting them to transient spectra and by comparison with the literature, electron distribution changes at the Fermi edge and hot electrons/phonons are identified as the main reasons for the changes. Probing at the inflection points of the LSPR reveals ultrafast signals. Using transient spectra they are traced back to a short blueshift of the LSPR.