This review provides an overview of the recent developments in the transmission of light through subwavelength apertures in metal films, with a focus on the phenomenon of extraordinary optical transmission (EOT) in periodic hole arrays. The key role of surface electromagnetic modes in the emergence of resonant transmission is highlighted, and these modes are shown to be responsible for both enhanced transmission and beaming effects in single apertures surrounded by periodic corrugations. The review covers both theoretical and experimental aspects, presenting results within a common theoretical framework, the coupled-mode method. It discusses the physical mechanisms operating in different structures and addresses several applications, including molecular sensing, spectroscopy, and photonic devices. The review also explores the extension of these ideas to other types of waves and speculates on future trends.This review provides an overview of the recent developments in the transmission of light through subwavelength apertures in metal films, with a focus on the phenomenon of extraordinary optical transmission (EOT) in periodic hole arrays. The key role of surface electromagnetic modes in the emergence of resonant transmission is highlighted, and these modes are shown to be responsible for both enhanced transmission and beaming effects in single apertures surrounded by periodic corrugations. The review covers both theoretical and experimental aspects, presenting results within a common theoretical framework, the coupled-mode method. It discusses the physical mechanisms operating in different structures and addresses several applications, including molecular sensing, spectroscopy, and photonic devices. The review also explores the extension of these ideas to other types of waves and speculates on future trends.