Groundwater is an important source of solutes from land to coastal waters. This input is most relevant even in areas where there are no continuous inputs through river channels. However, until recently, this input has not attracted much interest and studies have been scarce. The present work aims to show the importance of the input of metals associated with submarine groundwater discharge (SGD) in a coastal system such as the Ría de Vigo (Galicia, Spain). For this purpose, two samplings were carried out at different times of the year during the rainy (March 2024) and dry seasons (July 2023). Samples were taken from 8 intertidal subterranean estuaries, 7 wells and 3 rivers. In addition, coastal waters were sampled along the entire coastline of the estuary, and two central stations further away from the coast. Looking at the coastal samples, the levels of radon, a tracer of groundwater input, were three times higher during the rainy season. However, this input was only reflected in increased levels of Mn, Fe and Co, while the remaining metals (Ni, Cr, Cu, Zn, As, Cd and Pb) show a negative or no correlation with radon. Comparing the levels of metals between the three input sources considered in this study (wells, subterranean estuaries and rivers the highest values of Cr, Fe, Mn, Co, As, Cd and Pb were associated with subterranean estuaries, while the values of Ni, Cu and Zn were higher in wells. This study shows that the importance of metal inputs through SGD can be equal or greater in importance to inputs through rivers and is therefore a source to be considered when studying biogeochemical cycles of metals in coastal areas.