  In this proceeding, I discuss several models that extend the scalar sector of
the Standard Model by additional matter states. I here focus on results for
models with singlet extensions, which have been obtained recently and update
some of the results presented in previous work. In more detail, I will briefly
review the option to test a strong first-order electroweak phase transition
using precision measurements in the electroweak sector, as well as production
cross-sections for non-standard scalar production at Higgs factories.
