Last week, Moody's Investors Service surprised some observers by raising General Motors' (NYSE:GM) corporate rating to Baa3, the lowest tier that is considered to be "investment grade." Not long after the announcement, GM said that it would issue its first unsecured bonds since emerging from bankruptcy -- part of a debt-restructuring move that will save GM millions in interest payments every year.

Strong new products like the Chevy Impala are convincing more and more analysts that GM is on a major upswing. Photo credit: General Motors Co.

The upgrade is a big seal of approval for GM's current management team. But what does it mean for investors? In this video, Fool contributor John Rosevear explains how the upgrade will likely affect GM's financial position -- and what it could mean for GM shareholders over time.