Mooney M20S pilot reported a gear up landing.

Narrative

I departed ZZZ with a passenger to ZZZ1. I was going to pick up a pilot waiting there for us to bring him back to ZZZ. We were vectored for a VFR landing to XXR at ZZZ1 and cleared for a right base to final landing. The traffic pattern was busy and I became distracted and forgot to put my gear down which resulted in the incident.