Wiktionary
n. A metal wire that is encased in a thin strip of paper or plastic and is used to tie the openings of bags, such as garbage bags or bread bags.
Wikipedia
A twist tie is a metal wire that is encased in a thin strip of paper or plastic and is used to tie the openings of bags, such as garbage bags or bread bags. A twist tie is used by wrapping it around the item to be fastened, then twisting the ends together (thus the name). They are often included with boxes of plastic food bags or trash bags, and are commonly available individually in pre-cut lengths, on large spools, or in perforated sheets called gangs.
Usage examples of "twist tie".
After donning my protective gear, sans goggles, I opened the twist tie and emptied the uppermost bag onto the table.
Although the pouch itself was waterproof, almost every item inside it was further wrapped separately in a small plastic bag, fastened with a twist tie.
Lucy picked up a package of fat-free crackers and opened the twist tie.
A big chunk of space in the bag was taken up by her leather work boots, which were encased in a white plastic garbage bag tied with a twist tie.
After a minute, I got up, zipped shut the flap to my office, and secured it with a twist tie.