YOU SAID:

I met him by accident.

INTO JAPANESE

私は偶然彼に会いました。

BACK INTO ENGLISH

I had chance to meet him.

INTO JAPANESE

私は彼に会う機会がありました。

BACK INTO ENGLISH

I had the opportunity to meet him.

INTO JAPANESE

私は彼に会う機会がありました。

BACK INTO ENGLISH

I had the opportunity to meet him.