Metal seal, fluid control apparatus, and sealing method

A metal seal that is annular, provided between a first flat surface and a second flat surface, and sandwiched pressed by bringing the first flat surface and the second flat surface close to each other, the metal seal comprising:

• a first end surface part opposite to the first flat surface;
• and
• a second end surface part opposite to the second flat surface, wherein
• the first end surface part comprises
• paired first protrusions that are formed displaced in a radial direction of the metal seal and have dihedral angles in contact with the first flat surface, and
• the second end surface part comprises:
• a second protrusion that is formed on a radially inner side of one of the first protrusions and on a radially outer side of the other first protrusion in the radial direction, and has a dihedral angle in contact with the second flat surface;
• and
• paired third protrusions that are respectively formed on a radially inner side and a radially outer side of the second protrusion in the radial direction and whose highest points to which distances from a reference plane including the dihedral angles of the paired first protrusions in a direction perpendicular to the reference plane are shorter than a distance from the reference plane to the dihedral angle of the second protrusion in the direction perpendicular to the reference plane.