Read books, be in the countryside if possible, experience different types of weathers (it’s interesting how differently influenced you can be while it’s raining and while it’s sunny). My lyrics are very much inspired by my surroundings and even surroundings I imagine myself to be in (cold and grim mountains of Norway, ahhh).
One more thing, a particular event that happens in every day life can trigger you to write lyrics. Those moments happen very spontaneously and it feels like a stream of consciousness. Don’t try to fit the lyrics in a box, write whatever you feel at the moment.
These are some of the subjects I write about: mysticism, mythology, current world events, philosophy, inner struggles, wisdom, nature. I could post some lyrics if y’all want to see them.