  The third observing run of advanced LIGO, Virgo and KAGRA brought
unprecedented sensitivity towards a variety of quasi-monochromatic, persistent
gravitational-wave signals. Continuous waves allow us to probe not just the
existence of canonical asymmetrically rotating neutron stars, but also
different forms of dark matter, thus showing the wide-ranging astrophysical
implications of using a relatively simple signal model. I will describe the
major results from the numerous continuous-wave searches that were performed in
O3, both inside and outside the LIGO/Virgo/KAGRA collaborations, and show how
impactful to multi-messenger physics that they have been.
