$Meta Materials Inc.(MMAT)$ usaully, after dd, u buy into a stock and expect the share price to rise and/or the financial year end dividend will be substantial. So you decision is simple ie at an appropriate time and date taKe profit and run.. Which means you must monitor your stock and be aware of the cutoff price/ex div date, esp company announcement about probable m/a, in order to avoid being trap in this unfavorable position. 

In your case, notwithstanding your initial dwindling purchased price vs the new meta share price, as announced earlier, that it will be fixed for torchlight Friday closing price. At the end, it stood 9.90.

So what next? hope for good div pay out to help defry your loss and hope that the share price will move up in the near future, if the good review of the merged company will be reassuring... But again, too many hope armies around, your decision is to hold or not to hold that isthe question....even if Shakespeare is here, I don't think he help u! The decision is yours.. Do your dd!!