In the last few years, interest in long-lived particle signatures at colliders has been growing, but the field itself is still under-explored. This seminar will discuss the motivation for long-lived particle searches, particularly as they relate to Dark Matter models, give an overview of the methods and challenges involved, and talk about some specific examples from the ATLAS collaboration. Between the opportunities for technical improvements and the unusually strong dependence of analysis sensitivity on luminosity, these signatures are among the most exciting targets for the LHC Run 3. There is a lot of interesting work still to be done before the full potential of these searches will be reached!