From my personal point of view, there is nothing called the most important metrics, since brand management is done through integrated management framework or model that covers several perspectives, financial, Tactical, segment...etc such as Kaplan and Norton, or LOGMAN, though most of the time
Company Senior management will be interested to know the Compound Annual Growth Rate (CAGR) and Brand Manager will have to monitor the Brand Development Index
The key metrics that need to be tracked by brand manager in an automated buying environment includes traditional quantitative analysis such as reach . More importantly, qualitative analysis is needed to determine if the intended audience was reached in a receptive state, moving the brand needle. For example, brand mentions and share of voice relative to the perception change the brand was trying to create; engagement with distributed content plus time spent with it, and brand studies & respondent surveys. The bigger question to answer is 'what is a brand trying to do?' so you can serve up metrics that explain more then just the numbers and ultimately build brand equity."
