Being extremely suppressed in the Standard Model, rare decays of heavy-flavoured particles are a powerful probe of New Physics, and allow to reach energies beyond those accessible through direct searches. Several new results have been obtained by the LHC experiments. In particular, $b\to s l^+ l^-$ transitions give access to a large spectrum of observables, which provide complementary information on possible New Physics contributions. In this sector, tensions with Standard Model predictions have been observed.