What: Shares of Firstmerit Corp. (NASDAQ:FMER) have jumped as much as 22% in early trading Tuesday after it agreed to be bought out by Huntington Bancshares Incorporated (NASDAQ:HBAN), which has fallen 10%.

So what: The merger between the two banks will create the largest bank in Ohio with nearly $100 billion in assets. Huntington will pay 1.72 shares of its own stock and $5.00 in cash for each share of Firstmerit stock.  

The deal is expected to close in the third quarter and be approximately 10% accretive to earnings per share by 2018, the first full year after synergies are implemented.

Now what: Given the stock portion of this deal, it's natural that the two stocks will now trade in a related fashion. Firstmerit's pop shouldn't be a surprise because the deal is worth $18.67 per share with Huntington's shares currently trading at $7.95. But Huntington's drop is an indication that the market doesn't think the synergies both banks see as possible in a merger will play out as planned, which only time will tell.