Progressive metal is all about leitmotifs. Dream theater specially uses the technique to great effect. Like in Six degrees of inner turbulence or the meta album (each song in the album is in a different other album but construct a separate sequence) 12 step suite, about alcoholism.
I'll have to listen again but I don't recall 6doit having any recurring musical phrases that accompany characters or other ideas throughout the album. there is an overture at the beginning that introduces the songs.
It does, the overture doesn't only introduces later songs (through leitmotifs), it reuses them again for a reprise and a finale. Other examples include Metropolis part II: scenes from a memory, which is almost a musical, including characters, scenes and acts, and A change of seasons, where leitmotifs are not for characters but concepts.
A Thousand Suns by Linkin Park is a concept album about (nuclear) warfare and the threat of technology to humankind. It starts with an intro song in which the lyrics reference the penultimate song, The Catalyst. And that song itself has an intro track that references back to one of the first songs on the album, Burning In The Skies. The album connects itself back to front and the other way around.
Also, midway through the album, there's a track named Wisdom, Justice and Love, which features a speech by MLK, that gets progressively more distorted as it goes on, going from his normal voice to a completely robotic voice. In the intro to The Catalyst, the exact opposite thing happens, with the lyrics and melody going from robotic to natural sounding. Both these movements are a reference to the thematics of humanity vs. technology.
It's a masterful, underrated album. One of my favourites of all time.
Man, that album is so good that I almost want to say it would be worth learning German just to understand it, but I’m afraid even then then cultural references might be lost on people.
Definitely a masterpiece however. Every track just clicks right where it ought to, and the story that’s told (while ending slightly different from the canon version) is fantastic. Absolute 10/10, and I’m not even a goth or a metalhead.
The only thing I know with absolute certainty has a leitmotif (several, in fact) is Peter and the Wolf.
And maaaaybe Come to Daddy by Apex Twin. Does it count if the sound is literally generated by an image of the artist transformed into a WAV file? It literally represents them.