One of the hardest things to teach new traders is how to look for intermarket themes that move the stock market--and especially how to identify shifts in those themes. (See this example from early in the year and this later example). Themes are not constant and fixed; like the themes of a symphony, they appear with subtle variations, disappear, and reappear. A major reason that money managers like to keep in touch with their peers is that such communication keeps their ears to the ground, helping them remain sensitive to the presence, emergence, and changing of themes.
Recent themes have focused on economic stimulus, growth, and reflation, with emerging markets leading developed ones. That has led to strength in raw materials shares, as well as emerging market indexes such as EEM. When I saw that EEM was underperforming, that was an important alert at the top of a trading range. Similarly, the weakness in materials stocks this morning was an important indication of a thematic shift.
Many traders I work with will use information from a depth-of-market (DOM) display and/or chart patterns to frame short-term trades, only to get run over by thematic shifts they never see coming. You don't have to be a global macro trader to benefit from an understanding of the global macro themes that move markets.