After a second grand tour to continental Europe in 1737 and 1738, he returned to England in January 1739 and staged an opera, Angelico e Medoro, with music by Giovanni Battista Pescetti from a libretto by Metastasio at Covent Garden.
During that same year he came to London to join Handel's opera company, where he created roles in Handel's Ezio - with words by the renowned librettist Metastasio - and Sosarme, and sang in revivals of Admeto, Giulio Cesare, Flavio, and Poro.
Catone in Utica was the first opera that Metastasio wrote for the Roman public, and it was received with mixed feelings.
Most prominent of these is a long correspondence in the 1770s with Metastasio, the Italian court poet in Vienna and greatest librettist of the 18th century.
The early Metastasio texts he set were all greatly altered for the purpose, but Frederick the Great and Francesco Algarotti both exerted influence in order to make Hasse pay greater respect to Metastasio's works.
Like most theatre composers of the time, Portugal set several librettos that had proven successful for earlier operas, such as Metastasio’s Demofoonte (premièred at La Scala, Milan in 1794) and Artaserse; and he set many stories that had been used before, including Serse, Alceste, Adrasto, Semiramide and Sofonisba.
Romolo ed Ersilia ("Romulus and Ersilia") is an 18th-century Italian opera in 3 acts by the Czech composer Josef Mysliveček composed to a libretto by the Italian poet Metastasio first produced in Innsbruck in 1765 with music by Johann Adolf Hasse.
Writing his plays and opera librettos, Knyaznin often borrowed some ideas from Voltaire, Metastasio, Molière and Carlo Goldoni developing them and putting in different context.