I autopsied several of those little Chinese relays. The contact points are little balls of unknown metal. Sometimes they slide past each other, but still make a point contact.
Real relays for the power you want to switch will have circular contacts rather large in diameter. When new the surface is slightly convex and will be silver or silver plated. As the arcing progresses over time, the silver will be worn away and the contact area will be more flat. Also gets flat at the contacts are burnished with maintenance.
Paul