Cyanide is a highly poisonous chemical that can cause rapid death. In the song's context, Metallica compares the relationship to the effects of cyanide, as it leaves the protagonist weakened, consumed, and trapped. The lyrics express a sense of suffocation, with lines such as "Choking the breath from me, suffocating the only hope" and "Like cyanide in my blood, pumping through my veins."
The song also depicts a dynamic where the protagonist feels enslaved by the relationship. They are tormented by the feeling of being constantly held captive, unable to break free from the emotional torment:"Bound and gagged, with no escape, forced into this misery" and "Trapped inside this living hell, locked in a cold embrace."
Additionally, the track touches upon the idea of addiction and self-destruction. The lyrics suggest that the relationship has become a source of self-punishment, as if the protagonist is consumed by a self-destructive urge to remain within this toxic dynamic. Lines like "I'm sinking deeper into the ground" and "I'm drowning in the venom that's inside" symbolize the downward spiral caused by the relationship.
Despite the oppressive nature of the relationship, a flicker of hope emerges through the lyrics. The protagonist longs for a release from this cycle, represented by the line "Can't you feel the fire burning? Won't you save me from this yearning?." They desperately yearn for a way out and seem torn between the desire to escape and the pull of self destructive forces.
Overall, "Cyanide" by Metallica portrays a poignant and dark exploration of a relationship that has become deeply toxic and corrosive, leaving the protagonist trapped in a state of emotional anguish with a glimmer of hope for redemption or release.