From nylon to metal - there are many choices. Below are a list of the most popular more readily found.
Nylon Beading Thread
Used for beadworking and beadweaving. Slightly waxed. Use a beading needle to thread beads through nylon thread. Easy to knot and does not stretch much.
Thin strands nylon coated stainless steel wire of stringing cable coiled together to make a strong and flexible cord. Strong, and tarnish and corosion resistant. The larger the diameter, the stronger and more resistant to kinking the wire will be. Usually comes as a 7 strand or 49 strand wire. The 49 starnd wire is more stronger and flexible - it has a more supple drape, giving life and movement to jewellery.
Plastic stringing which is very easy to use. Simply make your necklace or bracelet and secure with a tight knot. Bracelets can be made to fit any wrist. Inexpensive choice as it does not require crimps, clasps, etc.
Large variety of sizes, textures and colours. Comes in round or flat design.