Form a technical perspective, heroic music is distinguished by various factors. For example, harmony changes. There’s a series of particular harmony changes most of us equate with an ‘heroic feeling’.
An instrument (or instrument family) being highlighted in its upper register. Oftentimes the climax has an adjusted meter of some kind, full of crescendos, cuts, highs and lows. Sometimes the music will go into a double-time feel, resounding with a lot of tension, and drama. There's often a common tone held over in at least one voice, but often is highlighted and emphasized by the composer.
Another very important aspect is the intensity progression. That is, how much of the spectrum is covered, how loud and clear the instruments are.
Action feeling is produced when there is a lot happening in music, so any sort of change will evoke the effect (chord change, timbre change, structure change etc.)
Besides, from an evolutionary standpoint, it is interesting to notice that heroic music will satisfy biological inheritance of acquired characteristics. It will be loud (to release adrenaline resulting in increased heart rate and blood pressure), the choirs will put emphasis on deep male voices or high female voices, to get us ready for the ‘battle’, and often very intrepid, to line up with our cultural understanding of the hunt and preparing us for battle.
In fact, heroic music is widespread in both video games and movie industries. Both sectors need arousing and powerful music, sprawling, instrumental passages. So, it doesn’t surprise anyone that this kind of soundtracks are frequently used by these businesses when they need to realize soundtracks for corporate videos, advertisements, video games, motion pictures trailers, action or epic movies etc.
Their goal is to make the player/audience/investor feel empowered by the soundtrack, to feel inspired by it and to identify himself or herself with the music itself. Resulting in a deep immersion in the mood of the movie, video game, advertisement etc.
So, if you want to advertise the trailer of an action movie or a new video game or even present a new company to potential investors, you would look for "heroic" music for your soundtrack.