Energy production still relies considerably on fossil fuels, and the building sector is a major player in the energy consumption market, mainly for space heating and cooling. Thermal bridges (TBs) in buildings are very relevant for the energy efficiency of buildings and may have an impact on heating energy needs of up to 30%. Given the high thermal conductivity of steel, the relevance of TBs in lightweight steel framed (LSF) components could be even greater. No research was found in the literature for evaluating how important the size and shape of steel studs are on the thermal performance of LSF building elements, which is the main objective of this work. This assessment is performed for the internal partitions and exterior façade of load-bearing LSF walls. The accuracy of the numerical model used in the simulations was verified and validated by comparison experimental measurements. Three reference steel studs were considered, six stud flange lengths and four steel thicknesses were evaluated, and five flange indentation sizes and four indent filling materials were assessed, corresponding to a total of 246 modelled LSF walls. It was concluded that the -value decreases when the flange length and the steel studs’ thickness increases, being that these variations are more significant for bigger flange sizes and for thicker steel studs. Additionally, it was found that a small indentation size (2.5 or 5 mm) is enough to provide a significant -value increase and that it is preferable not to use any flange indentation filling material rather than using a poor performance one (recycled rubber).