Create singable melodies on the guitar or synth. Even without lyrics, a strong motif gives the listener something to hold onto.
Incorporate mechanical or industrial sounds like clinking glass or metallic scraping to build a unique world for the listener. Rusty Nail - Instrumental
Ensure the song has a clear beginning, middle, and end. You can start "clean" and gradually add distortion (the "rust") as the track progresses. Create singable melodies on the guitar or synth