SARS-CoV-2 infectivity and inhibition involve the molecular interactions between oligomeric proteins, whether it is the trimeric surface spike glycoprotein, the dimeric cellular receptor (ACE2), or antibodies that by definition are dimeric. Yet, over the past few years, the traditional structural and biophysical approaches provided us with a simplistic picture of the involved interactions that is based entirely on a 1:1 interaction framework. Together with our collaborators, we present a new methodology based on mass photometry, single-particle tracking and a complete thermodynamic modelling framework to shine a light on the importance of multivalency and cooperative interactions in shaping biological function and regulation with emphasis on virus-host interactions and its neutralisation. Our results explain the real reasons behind differences in SARS-CoV-2 infectivity and inhibition, demonstrate that multivalency is central to shaping biomolecular mechanisms and, finally, we suggest a reasoning to the broad question as to why antibodies ‘look the way they do’.