This is the 13213th most frequent Russian word.
митрополиту
"Mitropolitu" in English means "to the metropolitan" (a senior bishop in Eastern Orthodox and some other Christian churches).
The word "митрополиту" is used here in the dative case, indicating the recipient of the action (sending the letter).
Вчера мы отправили письмо митрополиту с приглашением на праздничное событие.
Yesterday we sent a letter to the metropolitan with an invitation to the festive event.
Here, "митрополита" is in the genitive case, showing possession or relation (indicating whose request it was).
По просьбе митрополита организовали встречу с местными жителями.
At the request of the metropolitan, a meeting with the local residents was organized.
In this sentence, "митрополиту" appears again in the dative case, signifying the person to whom the matter was entrusted.