The shingle problem
Asphalt shingle is the default roof because it is cheap and quick. Its weakness is that asphalt is a petroleum product that dries out in heat and ultraviolet light. In the inland valley a standard shingle roof is often finished well before its rated life, curled and bald and shedding granules into the gutters.
The cost gap between shingle and metal has narrowed as oil prices moved, which is part of why metal keeps growing.
What metal does well
It lasts a long time. It does not curl, crack or lose granules. It sheds rain and wind-driven debris cleanly. It is light, so it does not stress an older deck. It is non-combustible, which matters in the foothills. And a light or reflective finish sends a lot of summer heat back where it came from.
It is also fully recyclable at the end of its life, unlike shingle which goes to landfill.
Wind, heat and fire here
Santa Ana winds lift shingles and ridge caps; properly fastened standing-seam metal does not have loose edges to catch. Summer heat ages shingle; metal expands and contracts but does not degrade. Embers from a foothill fire ignite dry debris on a roof; a metal surface with clean valleys gives them nothing to hold.
For the Highland and north San Bernardino neighborhoods those three points are the whole argument.
What holds people back
Upfront cost is higher than shingle. The look is not right for every neighborhood, and some associations restrict it. Installation needs a crew that knows metal, because badly detailed panels leak at the seams and expand into the flashings. And some people still believe the myths about noise and lightning, which I cover in another post.
None of those are reasons not to consider it; they are reasons to plan it properly.
Where it fits in the valley
Modern infill houses, ranch and horse properties, foothill homes with fire exposure, and any homeowner who intends to stay a long time and would rather roof once. For a 1970s tract house that will be sold in five years, shingle or a tile re-lay is probably the better money.
Ask, and I will tell you which side of that line your house sits on.