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.
[2] In 143-142 BC, when consul, he campaigned against the Celtiberians in central Hispania during the Numantine War, defeating the Arevaci, Lusones, Belli, Titii and the Vaccaei.
[5] In 133 BC, he gave a speech attacking Tiberius Gracchus regarding that tribune's plan to bypass the traditional prerogative of the senate and keep the vast fortune of the recently deceased Attalus III of Pergamon under the control of the Plebeian Assembly.
[7] His moralizing efforts awakened strong popular opposition, led by the tribune Gaius Atinius Labeo Macerio whom he had previously expelled from the Senate.
He was generally respected as the paradigm of the fortunate Roman for from an illustrious birth he united all manner of civil and military honours, and left a large family of four sons, of whom one was then consul, two had already been and one would be soon.