Urban metabolism is a concept employed to understand the flow of energy and materials through urban areas. However, applying this approach at the city level has been limited by the lack of data at this scale. This paper reviews the current application of the urban metabolism concept and proposes the concept of a “smart urban metabolism” (SUM). Through integrating ICT and smart-city technologies, the SUM model can provide real-time feedback on energy and material flows, from the level of the household to the urban district. This is highlighted through an example of its application in the Stockholm Royal Seaport, Sweden.