  After the discovery of the Higgs boson in 2012, particle physics has entered
an exciting era. An important question is whether the Standard Model of
particle physics correctly describes the scalar sector realized by nature, or
whether it is part of a more extended model, featuring additional particle
content. A prime way to test this is to probe models with extended scalar
sectors at future collider facilities. We here discuss such models in the
context of high-luminosity LHC, a possible proton-proton collider with 27 and
100 TeV center-of-mass energy, as well as future lepton colliders with various
center-of-mass energies.
