The answer to 'shower rusty water' is that rusty water in the shower is typically caused by corroded pipes or water heater components. This can happen as pipes and water heaters age, especially in homes with hard water or acidic water conditions. Symptoms include reddish-brown discoloration, metallic taste, and staining of fixtures.
The best solution depends on the cause. If the issue is isolated to the shower, you may be able to resolve it by flushing the shower head or replacing the shower valve. However, if the problem is throughout the home, it likely requires more extensive plumbing repairs such as replacing corroded pipes or the water heater. In this case, it's best to call a professional plumber to diagnose and fix the root cause.