The authors report the observation of high-quality-factor resonances in a planar metamaterial by introducing symmetry breaking in the shape of its structural elements. This approach enables the excitation of dark modes, which are weakly coupled to free space, leading to exceptionally narrow resonant responses in transmission and reflection. The metamaterial consists of asymmetrically split rings (ASR) arranged in a periodic array on a thin dielectric substrate. The resonant behavior is attributed to the excitation of anti-symmetric modes, which are forbidden in symmetric structures but can be excited due to the asymmetry. The quality factor of the resonances is significantly higher than in conventional metamaterials, reaching values of about 20. The results are supported by theoretical modeling using the method of moments, showing good agreement with experimental data. The study highlights the potential of dark mode resonances for achieving high-quality resonances in thin structures, particularly in the optical spectrum where losses are significant.The authors report the observation of high-quality-factor resonances in a planar metamaterial by introducing symmetry breaking in the shape of its structural elements. This approach enables the excitation of dark modes, which are weakly coupled to free space, leading to exceptionally narrow resonant responses in transmission and reflection. The metamaterial consists of asymmetrically split rings (ASR) arranged in a periodic array on a thin dielectric substrate. The resonant behavior is attributed to the excitation of anti-symmetric modes, which are forbidden in symmetric structures but can be excited due to the asymmetry. The quality factor of the resonances is significantly higher than in conventional metamaterials, reaching values of about 20. The results are supported by theoretical modeling using the method of moments, showing good agreement with experimental data. The study highlights the potential of dark mode resonances for achieving high-quality resonances in thin structures, particularly in the optical spectrum where losses are significant.