Identified almost a century ago by early quantum physicists, the study of bound states has become an active field of research that continues to surprise year after year with groundbreaking innovation opportunities and its connections to other research areas. Based on the physics of artificially engineered resonant metallic or all-dielectric building blocks (e.g., 3D and flatland metastructures), which can confine light at subwavelength scales and create high-density concentrations of electromagnetic energy, researchers are driving advances in nanophotonics and bringing us much closer to all-optical communication and data processing. In light of these, this thesis reports: (i) scalable plasmonic Fano-resonant metasurfaces for the generation of visible color and (ii) photonic quasi-infinite metastructures for refractometric sensing and sustainable chemistry. Chapter 1 discusses the limits and challenges associated with the fabrication of large-scale plasmonic metasurfaces because of fabrication imperfections, especially when using aluminum (Al). Chapter 2 demonstrates an all-dielectric metasurface design, made of periodic arrays of scatterers, towards next-generation thermo/photo-catalysis and refractometric sensing by exploiting the sharp resonances induced by bound states in the continuum (BICs), an intriguing concept in light-matter interactions.