Acoustic focusing (AF) enables the concentration of sound energy onto specific regions, traditionally relying on bulky curved lenses or reflectors. Recent advances in acoustic metamaterials, particularly ring-shaped structures, offer a compact and efficient alternative by harnessing eigenmode resonances to achieve high-intensity focusing with low input energy. This chapter presents a series of ring-shaped metamaterial systems for advanced AF applications. A brass ring immersed in water demonstrates perfect point focusing at its center, with potential uses in underwater detection and medical ultrasound therapy. Expanding on this, a multi-focus brass ring system exploits Mie resonances to create tunable focal patterns, suggesting applications in acoustic encryption communication. Furthermore, a dual-layer ring structure in air achieves diffraction-free focusing, suitable for acoustic beam splitters and directional transmitters. Finally, an eight-unit-cavity ring system exhibits exceptional robustness, generating a high-intensity focus via compound monopole Mie resonance while maintaining performance across varying incident angles and structural deformations. These designs collectively advance AF technology for sonar, medical treatment, secure communication, and energy harvesting applications.