tensorflow:Can save best model only with val_acc available, skipping

I know how frustrating these things can be sometimes..but tensorflow requires that you explicitly write out the name of metric you are wanting to calculate

You will need to actually say 'val_accuracy'

metric = 'val_accuracy'
ModelCheckpoint(filepath=r"C:\Users\reda.elhail\Desktop\checkpoints\{}".format(Name), monitor=metric,
                    verbose=2, save_best_only=True, mode='max')]

Hope this helps =)

To add to the accepted answer as I just struggled with this. Not only do you have to use the full the metric name, it must match for your model.compile, ModelCheckpoint, and EarlyStopping. I had one set to accuracy and the other two set to val_accuracy and it did not work.