"
You’re nothing but a cold heart covered in gold
That’s why, that’s why I’m leaving you
The writer obviously had their heart broken by a past lover, and the heart-breaker deceived him/her. They're unimpressed. They finally get sick of putting up with the falsity, the pretend games, and all the fake devotion and love. 'You're nothing but a cold heart covered in gold'. The person deceived their lover by pretending to be a loving and loyal companion, but that obviously turned out not to be the case.