A pilot can legally land without a METAR, and this happens all the time. The stations can and do go offline. Sometimes they break, especially after a severe storm. Many smaller airfields don't have on-site weather reporting, some others don't have a network connection.
You look at the closest available weather station and you look at the forecasts — human-authored (TAFs) and computer-autored (GFA/MOS). And when you arrive, you look outside at the actual conditions — the windsock, actual flight visibility, etc. If the conditions are worse than expected, you divert to your alternate.
You look at the closest available weather station and you look at the forecasts — human-authored (TAFs) and computer-autored (GFA/MOS). And when you arrive, you look outside at the actual conditions — the windsock, actual flight visibility, etc. If the conditions are worse than expected, you divert to your alternate.