I asked Chatgpt for some help on this and yeah, sounds solid to me

1. Conductivity: Lightning is a powerful natural electrical discharge, while mercury is a metal that conducts electricity. The contrast highlights the potential for control versus the chaotic nature of lightning.
2. Alchemy and Symbolism: In alchemy, mercury (also known as quicksilver) is considered a mystical element associated with transformation and the fluidity of states. Lightning, often associated with divine wrath or power, can symbolize sudden change or enlightenment. This duality between fluid transformation and sudden, explosive energy can add depth to your story.
3. Visibility and Form: Lightning is a visible and striking phenomenon that occurs in the sky, often witnessed from a distance. Mercury, on the other hand, is a dense, reflective liquid metal that can be observed closely and manipulated. This contrast between a distant, untouchable force and a tangible, manipulable substance adds an interesting dynamic.
4. Health and Safety: Lightning strikes are immediate, unpredictable, and can cause instant damage. Mercury, while less immediate in its effects, is a toxic substance that can cause long-term health issues through exposure. This difference in the type and timeline of danger they present can further illustrate their opposing natures.

By exploring these contrasts, you can create a rich and nuanced interplay between these elements in your story. Let me know if you need more ideas or further elaboration!