Metamaterials are photonic nanostructures which consist of an array of elements with a magnetic response (so-called "artificial atoms"). They influence light on a sub-wavelength scale, thus producing interesting far-field effects, for example negative refraction. To enhance these effects, the interaction between the artificial atoms has to be understood in detail. The aim of this Ph. D. project is to use the method of near-field microscopy to map the electric fields on the surfaces of our metamaterials with sub-wavelength resolution for wavelengths in the near-infrared.