The man required surgery to stem the bleeding and is still in hospital.

Luke Williams, 30, of Newcastle, was refused bail when he appeared in the ACT Magistrates Court on Monday on charges of intentionally inflicting grievous bodily harm and possessing an offensive weapon with intent.

Court documents said a number of witnesses heard yelling coming from a van in Hackett about 5pm on Saturday.

The defendant then allegedly chased his brother and struck him in the head with an electric guitar a number of times.

Police arrived soon after to find the alleged victim covered in blood and lying unconscious on the ground.

Williams allegedly told officers the man had attempted to run away from the car with the guitar when he fell and hit his head.

Williams was arrested, while the other man was taken to hospital.

The defendant applied for bail when he appeared before Magistrate Peter Morrison on Monday.

But prosecutor Vicki Hogarth opposed the application.

The court heard the defendant had a long criminal history, which included convictions for violence and failing to appear.

The defence said Williams could reside with his father in Melbourne and pay a surety to guarantee his reappearance before the court.

Mr Morrison refused bail and remanded Williams in custody to later this month.

Police are urging anyone who may have witnessed the attack or have any information that could help police to contact Crime Stoppers on 1800 333 000, or at act.crimestoppers.com.au.