Metropolitan Archbishops have specific duties given to them. While they are still bishop of their particular diocese and have all of the duties and rights afforded to that, they are also responsible (in the Latin Rite) for the following in regards to the dioceses in his Province (per Canon 436):
- To see that faith and ecclesiastical discipline are carefully observed, and to notify the Roman Pontiff if there be any abuses
- To conduct a canonical visitation if the Bishop of the diocese has neglected it
- To appoint a diocesan Administrator
- The Metropolitan Archbishop can celebrate the Sacraments in any parish in those dioceses as if they were his own, except for the cathedrals of those dioceses (he can if he gets permission)
But enough about Metropolitan Archbishops- what's a Pallium?!
Originally, a Pallium was particular to the Pope. The earliest that I've ever heard for reference to the Pallium is 220AD with Tertullian's On the Pallium (De Pallio). Around the sixth century (as far as I know), the Pope began to confer the Pallium on metropolitans. The specific origin is unknown, but such hypotheses include an investiture by Constantine; an imitation of the Hebrew ephod (the humeral garment of the High Priest); a mantle of St. Peter (which acted as a symbol of his office); a liturgical mantle (as this hypothesis goes, it was used by the early Popes and in the course of time was folded into the shape of a band0; a custom of folding the ordinary mantle-Pallium which was an outer garment in use in imperial times; finally, that it was introduced immediately as a Papal liturgical garment, which was not at first a narrow strip of cloth but a broad, oblong, and folded cloth. The Pallium is only supposed to be used during Mass and is considered a liturgical vestment.
In February, two lambs are blessed and their white wool is used to make the Pallium. The wool is then presented to the Pope and Sisters make the Pallium for the new Archbishops. The new Pallia are solemnly blessed after the Second Vespers on the feast of Ss. Peter and Paul, and then kept in a special silver-gilt casket near the tomb of St. Peter until used.
The celebration itself has changed in just the last century. Previous to Vatican II, the Pallium was formerly conferred in Rome by a cardinal deacon and outside of Rome by a bishop. The ceremony in both cases occurred after the celebration of Mass and the administration of an oath. After Vatican II, the liturgy for the conferral of the Pallium, and as it appears in the liturgical books, is supposed to take place at the beginning of the Mass in which the archbishop takes possession of his See. Pope John Paul II and Pope Benedict XVI have changed this practice (without a change to the liturgical books, as far as I'm aware). They actually summon all new Metropolitans to Rome to receive the Pallium directly from the hands of the Pope on the Feast of Ss. Peter and Paul.
Finally, Pope Benedict XVI has been known to wear a much different looking Pallium (you can read and see about it here). Join me in praying for Archbishop Gomez and the Holy Father (and my LSAT)