Prepreg, metal-clad laminate, and wiring board

A prepreg comprising

• a resin composition or a semi-cured product of the resin composition, and
• a quartz glass cloth,
• wherein
• the resin composition contains a modified polyphenylene ether compound terminally modified with a substituent having an unsaturated carbon-carbon double bond, and a crosslinkable curing agent having an unsaturated carbon-carbon double bond in a molecule,
• the substituent in the modified polyphenylene ether compound contains at least one selected from the group consisting of
• a vinylbenzyl group and
• a methacrylic group,
• the crosslinkable curing agent contains at least one selected from the group consisting of polyfunctional methacrylate compounds having two or more methacrylic groups
• in the molecule, and
• trialkenyl isocyanurate compounds,
• a content of the modified polyphenylene ether compound is 50 parts by mass to 90 parts by mass with respect to 100 parts by mass of the total of the modified polyphenylene ether compound and the crosslinkable curing agent,
• the prepreg contains a silane coupling agent having at least one functional group selected from the group consisting of
• a vinyl group,
• a methacrylic group, and
• an acrylic group
• in a molecule,
• a content of the silane coupling agent is from 1% by mass to 2.51% by mass, with respect to the prepreg,
• air permeability of the quartz glass cloth is 200 cm3/cm2/sec or less, and
• a cured product of the prepreg has a dielectric loss tangent of 0.002 or less at 10 GHz.