In a letter to be e-mailed to Obama supporters, the former vice president and Nobel Prize winner wrote, "From now through Election Day, I intend to do whatever I can to make sure he is elected president of the United States."
In 2000, Gore won the popular vote but lost the disputed election to George W. Bush, who captured Florida and its electoral votes after a divided Supreme Court ended the recount of ballots.
Since then, Gore has made combatting global warming his signature issue, and has been recognized worldwide for his effort - from an Academy Award to the Nobel prize.
Gore is one of the most popular figures in the Democratic Party, but he maintained a low profile in the primary campaign.
It's the second time that Obama has rolled out a major endorsement in Michigan, a state he did not campaign in during the primary because its election violated the party rules. Obama is counting on a win in Michigan in November, but brought Gore and 2004 vice presidential nominee John Edwards to help validate him among Democrats in the state after skipping their primary.
"It means a lot, obviously," Obama said of Gore's support, as he greeted workers outside the General Motors Flint Engine South plant. "He's somebody who is a visionary, not just for the party, but for the country."
Gore also asked for donations to help fund Obama's effort - the first time he's asked members of his Web site AlGore.com to contribute to a political campaign.
"Over the past 18 months, Barack Obama has united a movement.
He knows change does not come from 1600 Pennsylvania Avenue or Capitol Hill. It begins when people stand up and take action," Gore wrote. "With the help of millions of supporters like you, Barack Obama will bring the change we so desperately need in order to solve our country's most pressing problems."
Obama focused on his plan to improve the economy while in Michigan, which has the nation's highest unemployment rate. He told a crowd in Flint, which had a seasonally unadjusted April unemployment rate of 9.3 percent, that they cannot fear globalization but must embrace it as a reality of the future.
"At critical moments of transition like this one, success has also depended on national leadership that moved the country forward with confidence and a common purpose," he said.
