I am looking to write poetry for lyrics. Can anyone help?

I love darker stories, such as those of Lovecraft, and very much enjoy the writings of Mikael Akerfeldt. Often, though I cannot seem to find the words or develop a theme well.

So far, I find metaphors and irony play a big role, but also being somewhat vague helps too.

Any tips on the strategy behind writing poetry such as this, and specific ways to practice certain angles of the composition?

Thank you for your help!