Not Updated For Current Season
The masteries shown here are not yet updated for the current season, the guide author needs to set up the new masteries. As such, they will be different than the masteries you see in-game.
Braum is a strong lane support for he can protect his adc with unbreakable(E), he has decent mobility with stand behind me(W), and has good cc with Winter's bite(Q) and his passive concussive blows. Braum is also a good roaming support for these same reasons. In teamfights Braum should try to focus on protecting and peeling for the carries and getting his passive on everyone he can. Braum can even start teamfights with picking someone off with Winter's bite(Q) or with flashing and using Glacial fissure(R) to know up enemies, preferably a carry or two.