"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 bravo! in Italian means "You're good" in English.
Sei bella! in Italian means "You're beautiful!" in English.
"Six" in English is sei in Italian.
Tigrotta sei! in Italian means "You're a little tiger!" in English.
Perché sei arrabbiato? in Italian means "Why are you angry?" in English.
sei li?
"Are you safe?" in English is Sei salvo? in Italian.
"You are horny!" in English is Sei arrapato! in Italian.
"You are special!" in English is Sei speciale! 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.