Music

W.A.S.P.'s conceptual album "The Crimson Idol" plays with leitmotifs a bit: https://www.youtube.com/watch?v=qwnAzZF3_D8

The german gothic rock band ASP created the album Zaubererbruder, which is entirely about the folk tale of Krabat.

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.

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.

Hospice by the Antlers and Diamond Jubilee both immediately came to mind, both albums have recurring melodies and interpolations throughout

The Dear Hunter, acts 1 through 5.