  High-energy lepton colliders with a centre-of-mass energy in the multi-TeV
range are currently considered among the most challenging and far-reaching
future accelerator projects. Studies performed so far have mostly focused on
the reach for new phenomena in lepton-antilepton annihilation channels. In this
work we observe that starting from collider energies of a few TeV, electroweak
(EW) vector boson fusion/scattering (VBF) at lepton colliders becomes the
dominant production mode for all Standard Model processes relevant to studying
the EW sector. In many cases we find that this also holds for new physics. We
quantify the size and the growth of VBF cross sections with collider energy for
a number of SM and new physics processes. By considering luminosity scenarios
achievable at a muon collider, we conclude that such a machine would
effectively be a "high-luminosity weak boson collider," and subsequently offer
a wide range of opportunities to precisely measure EW and Higgs coupling as
well as to discover new particles.
