Rings are the most fundamental item in Sonic Rush. They serve multiple purposes: as your primary form of health, as a currency for extra lives, and as a significant contributor to your score. When you have at least one ring, taking damage will cause you to scatter your rings instead of losing a life. You can then quickly recollect some of the scattered rings if you're fast enough. If you take damage with zero rings, you lose a life. Collecting 100 rings automatically grants you an extra life, up to a maximum of 9 lives.
Beyond survival, rings are crucial for achieving high scores and S-Ranks. The more rings you collect, the higher your score. They also contribute to filling your Boost Gauge. In Special Stages, rings are the sole objective, and collecting a specific number is required to earn a Chaos or Sol Emerald. Always prioritize collecting rings, especially large clusters, as they are vital for both offense (via Boost) and defense (via health).