What are 'metal tiers' in ACA marketplace plans?

ACA marketplace plans are organized into four metal tiers based on actuarial value (AV) — the percentage of total healthcare costs the plan covers on average for a typical population. Bronze: ~60% AV (insurer pays 60%, members pay 40% through deductibles, copays, co-insurance); Silver: ~70% AV; Gold: ~80% AV; Platinum: ~90% AV. Higher metal tiers have higher premiums but lower cost-sharing. Catastrophic plans exist for those under 30 or with hardship exemptions, with very high deductibles. Silver plans qualify for cost-sharing reductions for households earning 100-250% of federal poverty level, which can effectively boost Silver to Gold or Platinum levels of coverage at Silver premium prices. The tier system helps consumers compare plans without needing actuarial expertise.