Photonic states with large and fixed photon numbers, such as Fock states, are crucial in quantum technologies but remain an experimentally elusive resource. A potentially simple, deterministic and scalable way to generate these states consists of fully exciting N quantum emitters equally coupled to a common photonic reservoir, which leads to a collective decay known as Dicke superradiance. The emitted N-photon wavepacket turns out to be a highly entangled multimode state, which makes its characterisation challenging, and its potential for quantum information an open question. In this talk, after reviewing the basics of superradiance and 1d waveguide QED, I will show that Dicke superradiant states have a high quantum Fisher information (achieving Heisenberg scaling), implying they enable quantum-enhanced metrology. Then, I will discuss possible effective descriptions of such states, which would allow a clean understanding of their properties.