Organisers of the Wacken Open Air festival in Germany on Tuesday asked fan to stay away as driving rain, rivers of mud, and traffic jams hampered preparations.
The giant annual outdoor event, billed as the world's biggest heavy metal festival, is set to kick off Wednesday, with 85,000 headbangers due to descend on the venue.
Although often a muddy affair, Wacken is facing severe accessibility problems this year, prompting both promoters and police to tell anyone who has not already arrived at the venue to turn back.
Organisers of the sold-out festival said the rain is expected to continue, with electrical storms possible, leading them to take the precautionary measures without calling off the event entirely.
Images ahead of the four-day festival showed early fans wading through mud on the site.
Some 150 bands, including Britain's Iron Maiden, US thrash metal act Megadeth, and folk punk group Dropkick Murphys, are due to play at the event over 8 stages.
On Wednesday, some of the ashes of Motorhead lead singer Ian "Lemmy" Kilmister, who died in 2015, were due to be brought to the fairground as part of an "unforgettable act" in his memory.
