We report a detailed theoretical investigation on how the nanostructures with headcaps based on gold nanorods can tune the optical properties and enhanced localized fields. The results show that the mushroom-shaped nanorods have great tunability in the NIR region and much stronger induced E-fields at visible and NIR wavelengths, and field amplification up to four orders of magnitude can be obtained, which will have great potential in photoinduced therapy and open a path to tune the optical response of nanorods instead of just changing the aspect ratio. (C) 2014 Elsevier B.V. All rights reserved.