Which technique involves securing gemstones with metal beads?

The technique that involves securing gemstones with metal beads is known as grain setting. In grain setting, small metal beads or prongs are used to hold the gemstones in place, allowing light to pass through the stones and enhance their brilliance. This method is particularly popular in jewelry design because it gives the piece a delicate and intricate appearance while securely fastening the gemstones.

The other techniques mentioned do not focus specifically on the use of metal beads for securing gemstones. Miniature painting involves creating intricate artwork on a small scale, typically on surfaces like ivory or enamel. Plique-a-jour refers to a form of enamel work that resembles stained glass, where transparent enamel is applied to a framework of metal. Champleve involves carving out channels in metal and filling them with enamel, rather than setting stones. Therefore, grain setting is distinct in its practical application of securely attaching gemstones with beads, making it the correct choice here.