The march was a demonstration of the "anger, frustration and disappointment" felt at the owners rejecting the rescue package, say organisers.
Workers at an aluminium smelting plant which is shutting after almost 40 years have marched in protest at the closure.
Anglesey Aluminium, on the outskirts of Holyhead, will close at the end of this month, with the loss of 500 jobs.
Joint owners Rio Tinto Group and Kaiser Aluminium said the increasing cost of electricity was forcing it to shut but had rejected a £48m aid offer.
Almost 100 people marched from the town hall to the gates of the plant in a rally organised by the union, Unite.
Regional organiser Graham Rogers said people accepted the "the fight is over" for preventing the closure.
The march was a demonstration of the "anger, frustration and disappointment" felt at the owners rejecting the rescue package, he said.
He said: "This is a clear case of a multinational company putting profit before people.
"That package was basically what it was going to cost in benefits over the next couple of years or so.
"The [UK] government and the Welsh assembly made it quite clear they were looking for a long-term commitment to maintain 350 jobs.
"[They] bent over backwards to help the company. The company were not prepared to buy into it."
He added that work prospects for those losing their jobs were "very bleak".
Anglesey Aluminium is the largest employer in north Wales, and the aluminium it produces is shipped all over the world.
It opened in 1970 and is a major electricity user. Its work has been closely tied in to an energy deal with the nuclear power station at Wylfa, 14 miles away.
But the station is due to be decommissioned and there were a series of efforts to secure the aluminium plant's future.