Brakes made a grinding noise, then the pedal went to floor.

Hello,

This sounds to me like you need to change the brake pads on your vehicle. The brakes on your vehicle have brake pads that are forced against a brake rotor attached to your wheels when you step on the brakes. When these pads wear down they have a soft metallic bar that will produce a squeaking noise to let you know it's time to change the pads. When they are completely worn out they will make a grinding metal to metal noise when the brakes are applied. At this point damage is being done to the rotor, and depending on how bad it is the rotor will either have to turned a lathe to smooth it out again, or replace the rotor entirely.
I have included a few links for you to go to down below:

https://www.2carpros.com/articles/brake-pedal-goes-to-the-floor
https://www.2carpros.com/articles/how-to-replace-front-brake-pads-and-rotors-fwd
https://www.2carpros.com/articles/how-to-replace-rear-brake-pads-and-rotors

I have also included a factory brake troubleshooting diagram for Accords in the diagrams below. Please go through these guides and diagram and get back to us with what you find out.

Thanks,
Alex
2CarPros