The gauge/gravity duality is a useful resource for studying the properties of strongly coupled systems in condensed matter physics and QCD, an example of which are strange metals: strongly interacting electrons that exhibit non-Fermi Liquid behaviour. In a weakly coupled neutral Fermi Liquid a sound mode is found at low temperature: zero sound. A somewhat similar, but different, mode is found at low temperatures holographically (strongly coupled!): holographic zero sound (HZS). This talk will discuss how sound modes and conductivity are calculated in the gauge/gravity duality, the importance of translational symmetry breaking (TSB) in modelling real systems and how TSB can be included in the duality with an outlook on its effect on HZS. Slides can be found here.