Lewis said in a Bloomberg television interview from the bank's headquarters that he expects Merrill will be "a thing of beauty" over the long term, despite losing $15.84 billion in the fourth quarter. "Everything we thought is playing out" with the January 1 purchase of the company, he said.
Some analysts have questioned whether Charlotte, North Carolina-based Bank of America overpaid for Merrill and took on too much risk when it bought Merrill and Countrywide, which had been the largest U.S. mortgage lender.
Many investors have worried that Bank of America could eventually be nationalized. Federal Reserve Chairman Ben Bernanke told Congress on Wednesday that the government had no plans for 100 percent takeovers in the industry, which would wipe out shareholders.
Bank of America shares closed up 43 cents, or 9.1 percent, at $5.16 on the New York Stock Exchange, after trading in a range of $4.20 to $5.50 during the session.
(Reporting by Jonathan Stempel; editing by Jeffrey Benkoe)