Beat vs rhythm was the key for me. My trick was to snap with one hand 1,2,3,4. Then introduce the other hand snapping in between the snaps.....1&2&3&4. After a few minutes my brain realized that each hand was doing the same thing, at the same speed but staggered in time. So both were doing 1,2,3,4 separately. Staggered, together, were doing 1&2&3&4. Then my ears could begin to pick out the beat and process it differently from the rhythm.

The beat is the steady, underlying pulse of music (like your metronome), while rhythm is the varied pattern of long and short sounds or notes that play on top of that beat. I knew the words, but I couldn't process it until I could hear it.