Mercury is second on our list of planets, ranked by apparent speed, after the moon. This is appropriate as Mercury, known to the Greeks as Hermes, is notoriously fast and was often known by his winged sandals and helmet. His speed made him, in a sense, the messenger of the gods. Mercury is the planet that rules communication between the worlds or realms. We will go into Mercury as a “god” more later, for now we will focus on his role in the heptarchia.
Mercury also rules communication in general. This means it has a special relationship to eloquence and refinement of the intellect, both of which are necessary for communication. Mercury shares many qualities with the element of air, in the sense that it is fluid, transportive, rapidly changing, and intellectual. Mercury’s fluid and changeable nature relates it to the zodiac sign of Gemini, which it rules over and shares many qualities with. Mercury’s intellectual nature also relates it to Virgo, which it also rules over. Don’t worry about memorizing these planetary and zodiacal associations right now, I’m just painting you a full picture of the nature of each planet.
The metal that Mercury rules over is quicksilver, which is now known primarily as mercury. Quicksilver, as the name implies, looks like a semi-liquid form of silver, which must have impressed our alchemical ancestors, and would have been indistinguishable from “actual magic” to most people for most of human history. This liquid metal perfectly fits Mercury’s nature as something able to rapidly change and defy attempts at containment. It is (at least was, in classical times) the only metal that can, at room temperature, literally slip through your fingers.
Here’s a gif of someone dipping a sponge into quicksilver (mercury):
Mercury rules over transportation, words, reason, and transmission in general. Mercurial things are highly refined, and can be elusive or even capricious. Its nature is generally rapid, unpredictable, and expressive. Its glyph (symbol) is a scepter or a rod, like the one carried by Mercury, which we know as the caduceus:
Here’s an image of Mercury with the caduceus, in case you’re unfamiliar:
It’s a rod encircled by two snakes, most often seen today as an emblem for hospitals or healing:
In legends this rod could wake the sleeping and put the awake to sleep. It is said that if applied to the dying they would be granted a peaceful death, and if applied to the dead it would restore them to life. One origin story for this staff illustrates the esoteric nature of Mercury:
Mercury (the god, not the planet) was walking along and saw two snakes before him locked in combat. He placed his rod between them and they became peaceful, circling around his staff.
Mercury, as a force that can swiftly transcend boundaries and create bridges between things, has a special role to play in conflict resolution and the reconciliation of opposites.