[yding]

Doubly true if it's outside market hours. Unlike every other broker Robinhood doesn't (always) warn you when the markets are closed. I've had fills come in dollars off the last trade simply because the market order was placed before or after hours.

[remote_phone]

Most places I’ve seen won’t allow you to place market orders after hours, only limit orders.

[astura]

Fidelity let's you do it, they just warn you.