In programmatic advertising, key metrics to track include impressions, click-through rates (CTR), viewability, conversions, and return on ad spend (ROAS). These metrics provide programmatic insights into ad performance, audience engagement, and campaign effectiveness. To measure success, compare performance against campaign goals and industry benchmarks, evaluate the cost-efficiency of impressions and conversions, and analyze attribution models to understand the impact of programmatic advertising on overall monetization in advertising.