"Six of Messina," "You're from Messina," and "You're (one of) Messina's" are English equivalents of Sei di Messina. Context makes clear whether the sentence's meaning references the role of sei as a cardinal number (case 1) or as the second person informal singular present indicative (examples 2, 3). The pronunciation will be "SEH-ee dee mes-SEE-na" in Italian.
Chi sei? in Italian is "Who are you?" in English.
Sei bella! in Italian means "You're beautiful!" in English.
Sei bravo! in Italian means "You're good" in English.
"Six" in English is sei in Italian.
sei li?
Perché sei arrabbiato? in Italian means "Why are you angry?" in English.
Tigrotta sei! in Italian means "You're a little tiger!" in English.
"You are horny!" in English is Sei arrapato! in Italian.
"You are special!" in English is Sei speciale! in Italian.
"Are you safe?" in English is Sei salvo? in Italian.
"You're in charge!" in English is Sei in carica! or Sei responsabile per...! in Italian.
Sei un cavallo! in Italian means "You're a horse!" in English.