Metrics can only get you so far. The primary method you have to contextualize what was going on when, and to correlate that with other events, is through logging. Metrics are always just a point in time, on a single given system. Metrics slice the cake vertically, but if you want a horizontal view across multiple systems, you need to integrate your logs.

Only by unifying your logging into your monitoring system and actively aggregating that information, can you start to get a complete picture of what is going on.

New Relic has been doing some good work in this space, and integrating logging information to their system is their single biggest area of growth right now.