How old is your child, and what causes their meltdowns? How much understanding of language do they have? You have to find the parameters your child can operate within, and work from there.
My DD is 4 and is very articulate, understands language v well, she has high levels of anxiety and responds aggressively when her anxiety is raised. She hits, bites, scratches and throws.
My DD's pan is is made worse by being restrained so we no longer touch her during meltdowns. We remove our other child from the room to a safe space and one of us stays with DD to ride out the meltdown.
We remove in advance heavy or breakable objects which can be thrown but otherwise let her throw as this helps release her distress. We hold a pillow over us to protect against hitting.
If there is a window to distract or soothe her on the way up or down from the meltdown we try that, sometimes it helps to break it and sometimes not.
We never leave DD alone in a room as she has separation anxiety and being alone terrifies her.
My DD tries very hard to control herself in public, and meltdowns outside the home are infrequent, but can be unsafe when they happen. In those cases I pick her up and carry her briefly eg away from a road, and try to find somewhere with more space but still contained while she rides it out.