If I'm thinking of the right advert and the song starts with what sounds like a sitar, followed by a rock intro, then the song is Wherever I May Roam by Metallica from their 1991 self titled album, which also has the nickname of the black album.
You can also find a classical/rock version of it on their 1991 double cd album 'S&M'. This is an album of some of their best known songs (and two new ones at the time), that they did as a collaboration in concert with the San Francisco Symphony Orchestra, conducted by Michael Kamen. If you don't usually listen to Classical music then don't be put off by this, the mix of the two styles and the resulting adaptations of the Metallica songs on the album, works really well.
Sorry for the rambling long answer, just thought I'd give you as much info as possible on places you can find the whole song.