Heavy Metal, also called Hebi Metako, is a small yellow robotic snake advisor. Don Harumage, the primary villain, gave this character to antagonist-turned-ally Da Cider in the original NG Knight series as a counterpart to the hero's advisor. Heavy Metal inhabits Da Cider's shoulder pads and performs the critical task of summoning the powerful Queen Cideron mecha when Da Cider plays a specific snake-charming flute.

The character displays steadfast loyalty and romantic affection toward Da Cider, frequently providing comic relief through exaggerated reactions to Da Cider's schemes and misfortunes. This dynamic endures after Da Cider's shift to ally, with Heavy Metal remaining his dedicated partner.

Heavy Metal continues as Da Cider's companion in the sequel series VS Knight Lamune & 40 Fire. The character retains its mecha summoning role, now supporting Da Cider as he co-pilots the Kaiser Fire mecha alongside protagonist Lamunade. Heavy Metal participates in critical events, including battles against the resurrected Abraham and a body-swapping incident.

The character is absent from the VS Knight Lamune & 40 Fresh OVA, which centers on new protagonists. Throughout all appearances, Heavy Metal consistently functions as a mechanical summoning device, provides advisory support, and engages in comedic interactions fueled by its loyalty and affection for Da Cider.