Are all angels holy and good?

No. All angels were once holy and revered God in heaven (Mark 13:32). The Scriptures make reference to some angels as "elect" (1 Timothy 5:21).

"When the Son of Man comes in His glory, and all the holy angels with Him, then He will sit on the throne of His glory" (Matthew 25:31).

" ;For if God did not spare the angels who sinned, but cast them down to hell and delivered them

"For we do not wrestle against flesh and blood, but against principalities, against powers, against the rulers of the darkness of this age,, against spiritual hosts of wickedness in the heavenly places" (Ephesians 6:12).