The Chalmers-Metcalf operator is a powerful tool in the theory of minimal projections. It was introduced by two American mathematicians Bruce Chalmers and Frederic Metcalf and applied in finding a formula for minimal projection from $$C_R[a,b]$$ onto the subspace polynomials of degree less than 2. During my talk, I would like to present various applications of this technique in the theory of minimal projections.