A metal roof ridge vent is easier to install than a shingle-over ridge vent because it's still necessary to cover a shingle-over vent with shingles, while the metal variety simply requires putting some straps in place to hold the vent steady. Other than that, the two types install almost identically.
Whether one is installing a metal vent or a shingle-over vent, the first step involves taking the shingle caps off and cutting the shingles away about an inch on either side of the peak. Beginning on one end of the roof ridge, the next step is to line up the first section with the edge and nail it into place, using 2-inch roofing nails and the pre-cut holes. The process continues, section by section, to the other side of the ridge, at which point the installer cuts the last piece to fit. Metal roof ridge vents merely require nailing straps into place between each section afterward.