You can place new orders during a trading halt, but new or existing orders will not be processed until the market reopens or the trading halt is removed. This applies to market-wide halts and halts on specific securities.
If you enter a “Good-til-Canceled” order and the market closes while a halt is in effect, your order will be held for execution at the opening of the next trading day. Additionally, orders entered as “Good for the Day” will be canceled at the end of the trading day regardless of whether a trading halt is in effect.
All new and outstanding orders will remain “pending” until markets reopen, or the trading halt is removed. When the halt ends, your orders will be processed. This also applies to options orders.