Market orders will fill, what a limit price does though is allow you to fill orders at or lower than what your limit price was set at depending upon the lot sizes. Market orders won't allow that. For example a market order at $.08 will always execute at $.08. But if you have a limit order in at $.08 and the price is $.081 and it drops to $.079 some may fill at $.08 and some may fill at $.079.
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