I love those like seven minute Metallica songs where there are structural changes that happen in the song, almost like different acts of the song rather than being one act.
https://open.spotify.com/track/51h0JFw6R8LQIB9q0GVdmG Actually multiple covers with great transitions, but this song does come to mind 🤘
Same. And Justice For All and Master of Puppets were phenomenal albums (same with for Ride the Lightning). For more recent, I like Avenged Sevenfold. They have some great long song with lots of structural changes (single: Tonight the World Dies)