Since its identification as an independent topic after the first world war, the chemistry of (bio)polymers and macromolecules rapidly benefited from intense synthetic activities driven by contributors focussing on formulation and structural aspects. Satisfying rationalization and predictions concerning polymer organization, stability and reactivity were however delayed until the late fifties, when physical chemists set the basis of an adapted thermodynamic modelling. The recent emergence of metal-containing (bio)organic polymers (i.e. metallopolymers) thus corresponds to a logical extension of this field with the ultimate goal of combining the rich magnetic and optical properties of open-shell transition metals with the processability and structural variety of polymeric organic scaffolds. Since applications as energy storage materials, drug delivery vectors, shapememory materials and photonic devices can be easily envisioned for these materials, the development of metallopolymers is faced to some urgency in producing novel exploitable structures, while the rational control of their formation, organization and transformation remains elusive. Caught between 2 the sometimes antagonistic requirements of economic efficiency on one side and of scientific pertinence on the other side, the ongoing achievements in the control of the metal loadings of multisite polymers are highlighted here with some tutorial discussions of luminescent lanthanidopolymers as proof-of-concept.