In this paper, a novel method to characterize the thermal dilatation of metals using a contactless measurement of the frequency-dependant reflection coefficient of a resonator is introduced. This wireless technique allows extracting the thermal expansion coefficient of the material without the need of any calibration. Two antennas, a VNA and a scatterer fabricated with the under-test material are required. All the measurements have been achieved using a climatic chamber with absorbers to control the scatterer's temperature. Measured values for thermal expansion coefficients are in good agreement with the values provided by the manufacturer which is confirmed by a sensibility study.