Fans clapped and chanted, while the Middlesbrough squad showed their support by warming up in SOS T-shirts.
Business Secretary Peter Mandelson has pledged £60m to help the area recover, but opponents have said the cash should be spent on saving the steelworks.
Middlesbrough FC chairman Gibson said that the closure would "rip the heart out of the Teesside community" and has insisted that the response from the government has not been good enough.
He said: "These are not just statistics, they are families, real people with mortgages, facing Christmas, and the ripple effect it will have right across the Tees Valley will be extraordinarily negative."
Mr Gibson claimed the knock-on effect of the plant's closure on businesses linked to the steel industry could lead to as many as 10,000 job losses across Teesside.
"The cost of that is far greater and far outweighs the cost of subsidising the steel industry for a short period of time, maybe one year. It doesn't make sense," he added.
Michael Leahy, general secretary of the Community union, will meet Lord Mandelson on Tuesday to call for further government support.
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