Is there wifi on the metro?
'Wifi' is pronounced WI-fi in Italian, stress on the first syllable, same as English.
Ask this when you need to use your phone underground without using mobile data. WiFi availability in metro stations varies greatly by city and line.
'C'è' (there is) + noun is the basic existential structure. 'WiFi' is used as an Italian word without translation. In Italian informal speech, prepositions are sometimes dropped with familiar loanwords: 'C'è internet?' works equally well.
Ho il segnale qui sotto?
Do I have signal down here?
Asks about mobile signal rather than wifi specifically.
Il metro ha la copertura 4G?
Does the metro have 4G coverage?
Specific mobile network question.
Funziona internet sui treni?
Does internet work on the trains?
Broader question covering both wifi and mobile data.
Milan's metro stations have free wifi provided by ATM (the transport company). Most Italian metro tunnels have no mobile signal, though investment in tunnel coverage is increasing. Download your maps and tickets before going underground.