Gault joins the Sky Blues after leaving Crusaders and has also formerly played for Linfield and Portadown.
Ex-Donegal Celtic player McAlorum was recently released by Glentoran, while Friars spent last season with Ards.
Defender Caolan Loughran has signed a new two-year deal and Allan Jenkins has been offered a new contract.
The three new recruits to the Showgrounds outfit have all agreed one-year deals.
"Supporters could see that evidently we strove last season to give youth a chance, but also as important is to strike a balance between youth and experience," said Ballymena manager David Jeffrey.
"Significantly we also wanted to add experience, not just in terms of playing in big matches, but also in winning trophies.
"Obviously this year we won our first, and got to Europe, and now we want to cement that achievement by adding experienced players such as the three we've brought in."
The Braidmen announced earlier in the week that they would be releasing six players, including forward Darren Henderson.
Ballymena United manager David Jeffrey has boosted his squad by signing midfielders Michael Gault and Stephen McAlorum, plus defender Emmet Friars.