Because it was a gift from Luna, creatures with rage are susceptible to silver. Fera that do not have Rage (such as the Nuwisha) do not suffer from this susceptibility to silver. Some of the Fera are instead susceptible to gold because they are devoted to Helios. The connection to Luna also affects how susceptible a Garou is to Frenzy based on the phase of the moon. A full moon causes a Garou to be very prone to their Rage overtaking them, while Garou are least suseptible to frenzy under the new moon.
Mechanically, Rage is rated from one to ten and comes in permanent (dot) and temporary (point) forms. Temporary Rage can be spent to gain extra actions or change forms. Temporary can be regained through strong emotions related to violence (such as physical danger) or by catching sight of the moon. It can go higher than the permanent rating only in rare circumstances.
Permanent Rage is rolled to try to regenerate wounds that would kill the Garou or to determine if he enters frenzy. Permanent Rage is often rolled to power Gifts. Permanent Rage is increased through spending experience points. Very few things will decrease permanent rage. The primary way permament Rage is lost is through aging.
If a Garou is out of both temporary Rage and temporary willpower, he loses the wolf. He returns to his breed form and cannot change shapes until he regains at least one point of each. He cannot regain Rage while he is out of Willpower. If he loses his last dot of permanent Rage, he will lose the wolf permanently.
The starting Rage of a Garou is determined by his Auspice. Ragabash start with the least Rage, while Ahroun starts with the most. Other Fera assign starting Rage based on other criteria. Spirits also use Rage, both as a substitute for physical attributes and as a means of powering their mystical charms.