Second-order Møller-Plesset perturbation theory (MP2) holds a unique place in the hierarchy of wavefunctionbased electronic structure methods. Historically, it was the first correlated method in quantum chemistry that was sizeextensive, invariant to unitary orbital rotations and computationally affordable. Until the development of modern density functional theory (DFT) it was therefore the workhorse method in molecular quantum chemistry. Even today, MP2 still plays an important role, e.g. in its spin-component-scaled variants or as a part of double hybrid DFT methods. Despite this popularity, the limitations of MP2-like methods are also well-known. In particular, they fail spectacularly for strongly correlated or metallic systems. Furthermore, a strong overestimation of dispersion interactions is observed for large polarizable systems, due to the absence of higher-order screening effects. With the significant recent interest in implementing and applying wavefunction methods to solids, MP2 is again at the center of attention as it represents the natural first step in such endeavours. However, the known problems for large and metallic systems clearly limit the usefulness of MP2 in this context. Indeed, canonical MP2 by construction must fail for metals, since vanishing band-gaps lead to diverging contributions to the correlation energy. Interestingly, coupled-cluster (CC) methods do not share this problem, despite being closely related to MP2. This improved behaviour can be interpreted as a renormalization of the band-gap due to the inclusion of screening effects. This makes CC methods highly attractive for condensed matter applications. Unfortunately, this advantage comes at a significantly increased computational cost.