In this study, the frequency selective surface (FSS), absorbance and sensing applications of new unit cells comprised of single, double and quad U-shaped metallic elements are numerically and experimentally investigated. The numerical results are realised by using finite integration technique-based electromagnetic simulation software, CST Microwave Studio. Experimental results are obtained by means of Agilent N5234A PNA-L vector network analyser. The simulated and measured results of U-shaped FSSs are carried out by using two different ways; periodic unit cell and waveguide boundary conditions. The single and quad U-shaped FSS elements show a single band-stop filter property, whereas the double U-shaped FSS shows a dual-frequency band-stop filter behaviour. Absorber and sensor applications of the proposed U-shaped FSSs are illustrated both numerically and experimentally. The three types of U-shaped FSS structures show a narrowband absorbance which has potential in biomedical and sensing applications. Single and dual absorber characteristics are observed with a 90% absorbance. For the sensor configuration, 800 MHz bandwidth is obtained for sensing different materials showing that it is possible to realise different microwave sensor studies in industries of food and agriculture. Simulated and measured results are compared for FSS, absorber and sensor configurations, and the results show a good agreement with each other.