Last month, the group announced they were teaming with the Welsh Blood Service “to give something meaningful back to the communities that welcome us”.
Alan Prosser, of the Welsh Blood Service, called it “a unique moment” for UK blood donation.
As well as working with the Welsh Blood Service, the band are working with England’s NHS Blood and Transplant (NHSBT) and the Scottish National Blood Transfusion Service to co-ordinate with dates at Glasgow’s Hampden Park and London.
It marks the first time the heavy metal veterans have collaborated with UK blood services, but follows a similar drive in the US and Australia.
Chris Risner, Metallica’s tour accountant who came up with the idea with band members, said he thought the idea would “see a lot of fruit” knowing the strong connection between the band and its fans but it had been “mind-blowing how big it has become”.
He he told BBC Radio Wales Breakfast that “giving back was important to the band… and the fans”.
“We just started it, and it took off to where it’s at now.
“[The band] are not surprised because they know how committed the fans are to this… knowing that the fans are such a massive community that adding any sort of blood donation to this band’s fans was a very simple connection in just introducing the two.”
Simon Campbell-Daves, of Welsh Blood Service, said the “Metallica family” had “come out in their thousands” to support the donation drive and help save lives.
“We cannot be any more thankful to them and to Metallica for their support in making this happen, it’s been incredible.”
Blood donation sessions, external are being held until 3 July as part of the M72 World Tour stop.
