In talking about grounding yourself by walking barefoot in the grass, woods or on the beach. Just a reminder of the energy in the earth and although it looks like lightning comes from clouds it actually comes from the earth to the clouds. So idf you want to allow the earth to re-energies you walk barefoot so it can flow from the earth into you.
Ay questions about where lightning come from just search it and you’ll discover what wa said above. This is the 1st step in Healing your body. Today I would say 99.99999 % of people never walk barefoot daily . You should everyday for about an hour and in a month tell all how you feel now vs., then.

You can also ground to tree trunks and dark crystals as well as being out in nature during or after a rainstorm

Yes, you can ,but, just walk in your yard barefoot everyday for an hour. I will show you a musician who you always is barefoot when he’s playing as he can feel the vibrations with his feets and the energy from the earth fills him and I believe thats why he plays so well.