This piece comes from Richard Wagner's opera "The Valkyrie", one of the four operas with the theme "The Ring of the Nibelung" (or "Ring Cycle" or simply "The Ring"). The "Ring" combines literature, visual elements and music in an innovative way for that period. We could say that this work was a precursor of the future films like "Star Wars".
Each of the 4 operas has its own love story and "The Valkyrie" is about the nordic story of twins Sieglinde and Siegmund, who separated in childhood, meet and fall in love. But their relationship is condemned by the gods who demand that Siegmund must die. Sieglinde and the couple's unborn child are saved by the defiant Valkyrie Brünnhilde, a powerful female warrior, who as a result faces the gods' punishment. This story is just a vehicle for Wagner to explore universal themes of love, betrayal, greed. The music describes the scene of the arrival of a group of female warriors, the Valkyries, riding on horseback above war fields and choosing who will live or die.
Perhaps the most famous use of this piece is modern days is in Francis Ford Coppola's film "Apocalypse Now". Parts of the music have also been borrowed by John Williams for his famous music theme in "Star Wars". The spirit of music is combative and heroic, conveying the power of the one who is fearless and spreads death around him.