In 146 BC, he defeated Critolaos of Megalopolis at the Battle of Scarpheia and the Arcadians at Chaeronea but Metellus was then sent to fight in the Achaean War to avenge an insult offered to a Roman Embassy at Corinth. He fought under the command of consul Lucius Mummius Achaicus whose ultimate victory in the war against the Achaean League delayed Macedonicus from celebrating immediately the honours of the Triumph which his success at the battle of Scarpheia merited. On his return to Italy he received the honour of a Triumph and the title of "Macedonicus". After his Triumph he built the "Porticus Caecilii" (which later became the "Porticus Octaviae") at the Campus Martius. He also built two grandiose temples: one dedicated to Jupiter and the other to Juno. These were the first marble temples in Rome, ornamented with equestrian statues of the various generals of Alexander brought by him from Greece.