These events are illegal, dangerous and often linked to anti-social behaviour and violence.
They also put those who attend at increased risk of Covid-19 as social distancing is all but impossible.
Officers attended several events on Saturday night and dispersed hundreds of people, largely without confrontation.
Commander Bas Javid, of Frontline Policing, said: “There are teams of officers dedicated to tackling unlicensed music events on duty tonight.
“These events are illegal, they’re linked to violence, and groups who hold them are breaching health regulations.
“Those who go to unlicensed music events are putting themselves, their families and their communities at risk. I urge anyone considering attending an event like this to re-think their plans.
“I would like to thank the many people who have reported unlicensed music events to police over the past two nights. I urge communities to keep helping police by continuing to report this illegal activity.”
The public can report suspected UMEs by dialling 101, by tweeting @MetCC or by calling Crimestoppers anonymously on 0800 555 111.