Fulminados comes from the verb fulminar, which means to strike down, annihilate, or blast. It's a strong, dramatic word that evokes a sudden, powerful impact.
In the song, Cerati sings, "Caemos fulminados por un rayo que viene del futuro" (We fall struck down by a lightning bolt that comes from the future). This vivid imagery suggests an intense, almost fated, and overwhelming experience, perhaps referring to the sudden and destructive force of passion or an unexpected turn of events.