Scalar extensions of the Standard Model provide simple yet phenomenologically rich models for BSM physics that can be looked for at current and future colliders. In my talk I will focus on the renormalizable scalar singlet extension and the relaxion as two benchmark models. Using these benchmarks I will discuss the various strategies needed at the LHC and future colliders to explore their vast parameter space. In particular I will discuss direct search strategies with prompt, displaced, and invisible signatures as well as indirect searches.