Quintus Caecilius Metellus Macedonicus was born as the oldest son of Quintus Caecilius Metellus and grandson of Lucius Caecilius Metellus. The Caecilii Metellii was one of the most important and wealthiest families in the Roman Republic. Although plebeians (not of patrician stock) the Caecilii Metellii remained a political power within the state, since 3rd century BC to the end of the Republic, holding every office in the cursus honorum as well as several important military commands.
He was a brilliant general that fought in the Third Macedonic War and would soon play a pivotal role in the Fourth. The fourth Macedonic War broke out because an adventurer, Andriscus, claimed to be descendent from the Macedonian dynasty, and was able to enter the Macedonian republic without serious resistance. He was successful enough in raising an army to defeat the first Roman force sent against him in 149 under the command of the praetor Publius Iuventius Thalna (who was killed). The second Roman army under Quintus Caecilius Metellus defeated the pretender in 148. Under his authority the country was made a Roman province.
In 146, he attacked the Achaeans to avenge an insult offered to a Roman embassy at Corinth. He gained decided successes over them at Scarpheia and Chaeroneia. On his return to Italy he received the honour of a triumph and the title of Macedonicus. He was elected consul in 143 BC when he defeated the Celtiberians in Northern Spain and reduced them to obedience.
In 131, when censor with Q. Pompeius (they were the first two plebeian censors), he proposed that all citizens should be compelled to marry in order to increase the birthrate, a law that was never put into practice. He expelled a number of senators, one of whom, the tribune C. Atinius Labeo, proposed that he should be hurled from the Tarpeian rock; his life was only saved through the intervention of another tribune.
He was an opponent of the Gracchi although not averse from moderate reform. He was a strict disciplinarian and he erected a splendid colonnade in the Campus Martius (PORTICUS METELLI), and two temples dedicated to Jupiter Stator and Juno. It was between the circus Flaminius and the theatre of Marcellus, and contained many works of art.
It was later removed to make room for the PORTICUS OCTAVIAE. Quintus Caecilius Metellus Macedonicus died in 115 BC.