Kagome-lattice metals provide a platform for investigating how lattice geometry, magnetism, and electron–electron interactions combine to produce unconventional electronic structures. Among these materials, the metallic antiferromagnet FeSn has attracted particular attention due to its flat electronic bands, Dirac crossings, and correlation effects. The study builds on recent results obtained using angle-resolved photoemission spectroscopy (ARPES) and their direct comparison with electronic structure calculations using density functional theory and the Korringa–Kohn–Rostoker (KKR) Green’s-function method. After introducing the essential band-structure motifs of kagome systems, the analysis focuses on FeSn, highlighting the phenomena of flat-band splitting and selective band renormalization observed in ARPES and captured by theory. The analysis highlights how symmetry, electronic correlations, and magnetic order shape the band structure of FeSn, and how these effects manifest in both theoretical calculations and ARPES measurements.