Magnetorheological elastomers (MRE) are smart materials whose modulus or mechanical performances can be controlled by an external magnetic field. In this chapter, the current research on the MRE materials fabrication, performance characterisation, modelling and applications is reviewed and discussed. Either anistropic or isotropic or MRE materials are fabricated by different curing conditions where magnetic field is applied or not. Anistropic MREs exhibit higher MR effects than isotropic MREs. Both steady-state and dynamic performances were studied through both experimental and theoretical approaches. The modelling approaches were developed to predict mechanical performances of MREs with both simple and complex structures. The sensing capabilities of MREs under different loading conditions were also investigated. The review also includes recent representative MRE applications such as adaptive tuned vibration absorbers and novel force sensors.