Think of songs you like that used a sampled instrumental from the past and then injected into a newer song.
Take these songs for instance:
This one sampled the "Sweet Child O' Mine" guitar. A pumped, hip-hop beat and rap vocals intertwined with the guitar, giving a different, unique sound. Mike Shinoda, known as part of the former group, Fort Minor, and a current member of Linkin Park, has a great ear in my opinion.