In Fahrenheit 451 by Ray Bradbury, where does bravery and loyalty play an important part?

Guy Montag lives in a world where no one can be trusted because people are trained to turn someone into authorities for possessing or owning books. It doesn't matter what relationship a person shares with another, either. Children can turn in parents, neighbors turn in neighbors, and even a wife can turn in a husband simply for looking at a book. The consequences are arresting the offender and burning down his or her house along with the books. In order to live in such a society, one would need to be brave and loyal to one side of the issue or the other. Book owners would need to be brave to face such a society and loyal to others whom they know own books, too. On the other hand, non-book owners would have to be brave enough to turn in family members, friends, or neighbors in order to remain loyal to the government. The scary part is discovering who might be brave and loyal for whom. Either way, a person must be brave and loyal in order to survive this life.

As Montag switches his loyalties away from supporting book burning, he must brave the consequences of his choices and actions and discover whom he can trust. He tries to bring his wife along with him in this endeavor, but she turns on him and calls the authorities, instead. Montag realizes his wife's betrayal as he shows up to his own house with the fire squad:

"The front door opened; Mildred came down the steps, running, one suitcase held with a dreamlike clenching rigidity in her fist, as a beetle-taxi hissed to the curb.

'Mildred!'

She ran past with her body stiff, her face floured with powder, her mouth gone, without lipstick.

'Mildred, you didn't put in the alarm!'" (114)

To his surprise, his wife was neither brave nor loyal--she simply fled. Hence, bravery and loyalty are important here because his wife didn't have either to support her husband. 

Later, Montag bravely runs for his life. The Mechanical Hound is sent out after him and he has to escape into the river to avoid it. Luckily, others like Montag who live in the wilderness were loyal and did not assist the authorities to find him. Instead, they helped Montag by bringing him into their midst and accepting him. Granger, the leader in the wilderness, explains their role in helping Montag:

"Granger nodded to a portable battery TV set by the fire. 'We've watched the chase. Figured you'd wind up south along the river. When we heard you plunging around out in the forest like a drunken elk, we didn't hide as we usually do. We figured you were in the river, when the helicopter cameras swung back in over the city. Something funny there. The chase is still running. The other way, though'" (147).

Oddly enough, strangers were more brave and loyal for Montag than his wife was. If these people had not gone to help him, Montag could have died alone in the wilderness. Lucky for him, though, he finally finds people with whom he shares a common interest in preserving the thoughts, stories and ideas found in books and they live to wait for a time when they can share those things again.